Here is Jen Agg up in arms (not for the first time) on April 14, 2017. In answer to a three-star Toronto Life review – three stars! very good! – of Grey Gardens, the fifth and newest gem in her small but sparkling crown of beyond-hip restaurants and bars, the most controversial restaurateur in Canada is, over two days, snapping out nearly 150 tweets.

She started punching before eight this morning, and won't stop until after 11 p.m. In the meantime, she's publicizing her new book I Hear She's a Real Bitch and steering three other successful drinking and eating establishments (Rhum Corner and Cocktail Bar in Toronto, Agrikol in Montreal), all while reopening The Black Hoof, the miraculous restaurant that made her famous when she introduced Toronto to tip-to-tail eating.

The tweets are not for the faint of heart. (Agg tweets seldom are.) "Honestly I'd really like to (JUST ONCE) be judged solely on my work in a review," she types in one. In another she praises one local restaurant and disses all the others ("they are the ONLY local restaurant owners who've had the courage to show me any support for this TL nonsense"). She demands retractions and apologies.

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The reviewer raved about the food of Grey Gardens chef Mitch Bates, a former mainstay at David Chang's Momofuku empire and now Agg's business partner in the restaurant, but took issue with Agg's décor and her personality, her talent for controversy. In Agg's view, this is restaurant-business sexism as usual – praise the man, slag the woman. "The review attributed all the positive experiences of the restaurant to my partner," she says. "And said that it was all in spite of me. And that's crazy. Because everything here is me."

But by day's end, thanks to her 13,400 Twitter followers – her "support network" – she has reaffirmed her role as defender of women in the food industry, and exponentially multiplied the publicity value of a three-star restaurant review into a five-alarm blaze.

Upping the ante is something Agg does. One famously busy Saturday night at the Hoof in 2011, she tweeted "Dear (almost) everyone in here right now … please, please stop being such a douche." Her reputation for confrontational insouciance – or inhospitable bitchiness, if you count yourself among the crowd she is mocking in the title of her book – has not abated since. Agg's conclusion: "It's always felt like the city is quick to hang me for even a whiff of arrogance while they encourage and applaud ego and macho swagger in my male contemporaries."

She wades in on gender and non-gender issues alike. She recently countered a National Post list of "hot" trends in food (it included craft beer and sustainable seafood) with withering sarcasm: "UM WHAT YEAR IS IT???"

She once told a group of Newfoundlanders at her first bar, Cobalt, that they couldn't have rum and cokes: Cobalt didn't do rum and coke, at least not that dull old way.

"She is everything loathsome about the new Toronto," a long-time patron of her bars told me. "She also makes the best cocktails in the city by far, and I've tried them all."

All these assertions are made off the record, because her critics are terrified she'll flambé them tableside on social media.

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"Maybe the reason why Jen doesn't get the respect she wants," Grant van Gameren, her former partner at the Hoof, says, "is because she's too much of a bully."

Agg's reluctance to coddle cantankerous customers isn't just pique, either. She's the tip of a new generation's philosophy of hospitality, one that believes in overturning the conventional wisdom that a paying customer is always right – "an anachronism," she writes, "so ridiculous it's shocking how many people still hold onto it so dearly."

All Agg's methods are radical. But they raise interesting questions. Is her outspoken feminism essential to her value as an owner precisely because it challenges the status bros of foodland? Likely. Or is she just another egomaniac with a genius for making sublime restaurants? Also very likely.

Here is Jen Agg at her post at Grey Gardens, leaning against the antique sink between the bar and the lively kitchen counter. She rarely rests when she's hosting the floor: chats with guests, clears tables, carries drinks, pivots. The staff – young, attractive, casually attired – are forbidden from saying both "You still working on that?" as if they were conversing with a pit of plumbers, and "Hi, I'm Darla, I'll be taking care of you tonight," because Agg always imagines a patron replying "Does this come with a hand job?" She likes the table to be wiped between every course and again before the bill is dropped.

David Greig, her partner in what will eventually be a pub in the basement of the Grey Gardens building, is concocting cocktails like a sorcerer's apprentice. Her sommelier and general manager, Jake Skakun, is plucking wines from the restaurant's mind-opening list. The majority of cooks in the kitchen are men, even here. Agg says this is the result of a shortage of women coming into the business, which she feels only proves her point about its structural sexism.

And the crowd at Grey Gardens? Hipster Supreme: eclectically dressed women in their thirties out-number slim-trousered, besweatered men, two thirds of whom have exactly the same furzey beard (the no. 2 setting on the clipper after days of growth). No one colour of skin predominates amongst the clientele at Grey Gardens, which gives the restaurant a hopeful feel. They're the young downtown elite, couples who can afford $200 dinners – although Agg has lowered the standard three-times markup on wine so more customers will try the restaurant's wide-ranging list.

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The room is peaceful and original, elegant but relaxed, its grace pulled from, but somehow mindful of, the rubble of the original space. She spent nearly $500,000 to make it this way. Agg and her husband, Roland Jean, a painter originally from Haiti, respectively designed and made the lights suspended over the kitchen counter, which set off an eclectic collection of decanters and table lamps. An entire wall of gray-green botanical silhouettes, palms and ferns and colocasia drawn free-hand directly onto the white-washed cinder block wall give the room the air of an artfully primordial jungle.

These were all Agg's decisions. "I like the colour grey," she says. "I like the ambiguity of it." Unlike her Twitter feed, which bristles with certainty, the room refuses to be pinned down. Even the security gate drawn permanently across the front window is a statement: It hints at safety, by fencing off the outside world. Grey Gardens is Jen Agg's refuge.

The food is spectacular. Spalls of rutabaga, endive, watercress and cheddar make a perfectly balanced salad, the sourness of the turnip working off the sharpness of the cheese like a good-natured argument. Agg suggests a rare sake, a perfect synch. The plates by Mitch Bates and his chef de cuisine, Peter Jensen, don't feel like meals so much as a series of short stories by a brilliant new writer you should already be reading. Jen Agg knows how to run a restaurant.

"I believe she is incredibly talented, incredibly prescient, especially for the Toronto market," one long-time industry insider says. "Jen looks at the restaurant scene and sees the shortcomings, and does something about it." She did it when she reinvented meat-eating at Black Hoof, with postnuclear cocktails at Cobalt and Cocktail Bar, with heaven-tender griot from Haiti at Rhum Corner and Agrikol (in which her partners are Win Butler and Régine Chassagne, founding members of the band Arcade Fire), with the idea of a prewar Parisian wine bistro at Grey Gardens. She has been a huge success, five times, in a notoriously competitive and sexist business. Just to open the doors at Gray Garden costs her $1,500 in wages. The wait for a table is pushing three months (the bar is saved for walk-ins). One member of her team estimates the restaurant is clearing $12,000 a week in profit – or what will be profit, once the build is paid off. Agg refuses to disclose the tricks of her trade, but there are signs that, at Grey Gardens, with new partners, she is exercising a financial and managerial discipline she had yet to learn in the looser early days. After her first bar, Cobalt, collapsed in 2006, she owed $300,000 in back taxes and declared bankruptcy.

The font used for Grey Gardens' name is faint lowercase grey handwriting, suggestive of a desire to disappear, which Agg sometimes admits to. "I don't like people," she says, even as she works to please them. She is not afraid to contradict herself.

She spent three hours today at the as-yet-unopened Black Hoof, testing recipes. At some point she posted a picture of herself as a teen – skinny, tall, not shy. She has long brown hair and wears a lot of grey. Tonight she's wearing tight white pants and has her ever-present phone in her back pocket.

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Gradually, as the restaurant's hubbub subsides a little after 9:45, Agg allows herself a glass of wine. She's wary, sometimes to the point of suspicion, and famously impatient: An innocent question about the hand-painted wall brings the response, "Are you trying to wind me up?" It's the tension of running a restaurant for hours on end, the strain of trying to please as many people as possible without evaporating in the process. Earlier today, her husband texted her: "I miss you so much." She texted back, "I miss you too, but you can't do that to me," by which she means make her feel bad for not being with him while she works (incessantly).

She is, but she insists she does not want to be, a spokesperson for her industry and her gender. "So why don't you just shut the fuck up?" she says, asking and answering her own question. "Because I don't want to do that either. I like saying stuff, I just don't want to say it from a politically roped in position." Pause. "The truth is, what you see is what I think in the moment."

Here is Jen Agg, preparing to publish her memoir, I Hear She's A Real Bitch, next week.

The book was the brainchild of Kristin Cochrane, president and publisher of Penguin Random House, who – this is rare – asked Agg to write it the same evening they met at Cocktail Bar. Cochrane was looking for the next Blood, Bones & Butter, the best-selling memoir by Gabrielle Hamilton, owner of Prune, a tiny perfect restaurant on Manhattan's East Village. "Of all the food memoirs," Cochrane says, "that's the one that stays with you."

Agg's book chronicles her youth in the suburban sameness of Scarborough during the early Bernardo years, and her desire to escape as a teenager – a desire that propelled her out at night, downtown, through her first marriage to Tyler Taverner, with whom she owned the avant-garde cocktail bar Cobalt, and into her marriage to Roland Jean and the heart of the hipster restaurant business, where she advertised on Craigslist for a charcuterie chef and found Grant van Gameren, in 2008. When Agg and van Gameran parted ways at the Hoof in 2011, the unspoken question was who would survive.

Both have, in uncannily parallel ways. They're both demanding perfectionists, both neurotic, detail-driven … curators is the only word for it … of restaurant experience. She also devotes 60 pages of her book to her battles with van Gameren, accusing him of being a sexist control freak who couldn't acknowledge her front-of-house importance to their restaurant. According to Agg, he dismissed cocktails and assumed that, because she wasn't sweating in the kitchen, she was out shopping. By the end, they were bickering non-stop. During one exchange, Agg told van Gameren he had to find a therapist to get over his mother issues – his died when he was 11. Van Gameren (who followed Agg's advice) has gone on to create a bevy of booming bars and restaurants in Toronto (Bar Isabel, Bar Raval, El Rey), as has Agg (with the exception of Raw Bar, her ambitious seafood venture that closed a year after it opened). But they still don't get along.

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"She's really passionate," van Gameren says, in a rare break from his vow of public silence on the subject of Agg. "A bold and risk-taking personality that I gravitated towards. The Hoof was an amazing experience. But at times, I felt I was distancing myself from her because it was hard for me to be viewed, essentially, as one identity when, quite frankly, our views on hospitality were so different." She let fly at customers, wine merchants, clients. "My whole thing is that we are in the hospitality business," van Gameren continues. "Customers and suppliers alike deserve a certain level of respect. From my experience, that was only her approach if she deemed you worthy from the get-go. That was one of our fundamental differences."

The most common complaint you hear about Agg from bros in the city's kitchens isn't that she's wrong about sexism in the restaurant business – but that her complaint is too broadly aimed at all white men. "Many white men I know that support her ideals find her comments offensive," van Gameren says. "I believe there are good people and bad people. I think we need to spend more time highlighting the progress these good people are making. Change doesn't happen overnight and she intimidates people to the point that they will stay silent with fear of possibly not getting it perfect."

And yet, Agg is a role model to an entire generation of young women in the restaurant business, and then some. When former pastry chef Kate Burnham launched harassment allegations against Weslodge ("a Toronto restaurant of dubious distinction," according to Agg), Agg organized an international conference on the sexual abuse that's daily fare behind the pass-through of most restaurants. Kitchen Bitches: Smashing the Patriarchy One Plate at a Time broke the industry's institutional silence, and established Agg's reputation as a crusader.

It also earned her death threats from men's rights activists. But she doesn't intimidate easily. Durga Chew-Bose, a Montreal-born, Brooklyn-based essayist, sees Agg's nonstop outspokeness as a form of generosity. "She's just had to work harder than most of the men. I mean, she must have, it's such a male-dominated industry." Agg's controversial status is the result of her "not being silent. From not just taking up space, and not being silent."

Saying what one thinks, which Agg knows how to do, is not the same as being forthright. For all the full-frontal revelations in I Hear She's a Real Bitch – Agg gets caught with her mother's vibrator, cheats with her best friend's boyfriend, admits she's better friends with men than women, etc. – the book, like its author, can be stingy with genuine emotional candour. Agg is very smart, very funny, and terrific on the antics of running a restaurant, but she prefers pronouncements – a style honed in her 20,900 tweets – to detailed scenes of emotional revelation that might upend a memoir's intellectual certainties and make it less predictable. But the cracks that let the light into her story are there, if you look carefully.

On page 133, by which time Agg is well into her 20s, she reveals for the first time that she was born with Poland Syndrome and thus only one breast. She had corrective surgery at 16, but will tell you that some evidence remains. "As a teenager," she writes, "this was a source of much conflict and resentment." That and a handful of paragraphs are all she devotes to a formative affliction, the kind of chip not on her shoulder that drives her fierce and admirable desire to be accepted as she is, and not as she is supposed to be. The moment Roland – who was 49 at the time, to her 29 – first sees her body in the shower, and instantly accepts her, is the moment she falls in love with him. "I respected him so much, I reasoned that if he found me beautiful, maybe it was true. Which doesn't sound very feminist, but it was the thing that helped the most."

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Here is Jen Agg having dinner with her husband Roland Jean at Scaramouche, an old-style, customer-is-always-right nook at the foot of Forest Hill in Toronto. In his company she's a different, less anxious person: Her voice lightens and she laughs more. Maybe, like a lot of people, she is her truest self in the company of her partner. He doesn't drive, so she drives him – and texts for him and "suggests" what he might want to order (the pepper steak with pasta).

Their conversation winds on for hours, through their respective origins (she boldly maintains her upbringing in Scarborough was riskier than his as a political cartoonist under Papa Doc Duvalier and the Tonton Macoute in Haiti, where his life was in danger); the history of their business partnership; a standoff over Beyoncé and whether she is good or bad for feminism (Agg says bad, but admires her as a role model for young black women; Roland insists she exploits the artists who create her public image); their common enemy (older white men); his global haziness on dates and details; her intergalactic stubbornness. Eventually she admits that sometimes when she wants to tweet – she actually has a draft tweet file! – Roland convinces her not to.

"He's a better thinker than I am," Agg says. "I get that. I'm too angry to think clearly sometimes. At the end of the day, I cannot have conciliatory conversations with people whose beliefs clearly and fundamentally do not line up with mine in a certain way. I can't handle it."

She finds it shocking that some people think she provokes public outcry intentionally, à la Trump. "The intention is not necessarily to be provocative. It's to be direct. I really do mostly come from the heart. I'm an instinctual gut person. And I don't fully think things through sometimes. And sometimes I say dumb shit. It's true."

"You never say dumb shit," Roland offers, casually, in his deep French-Haitian accent. Jen's afraid he is going to fall asleep. This is the third time she has dragooned him into attending a publicity interview. He claims it's the last. "You're just not a diplomatic person."

"How kind of you. I'm not a politician, that's true. I try sometimes."

"She never tries."

"Thank you, honey."

Every morning when she walks down the steps of their house – every single morning – Roland stands at the bottom and grabs her by the waist and lifts her off the last step. Given that he is 20 years older, a day will likely come when he is not there to catch her, a possibility she does not relish. I Hear She's a Real Bitch is dedicated to "Roland, without whom I'd die."

Here at last is Jen Agg, curled in the corner of the Sam James coffee bar on Queen Street West, a block south of where she lives, in the heart of downtown Toronto. Coffee is her first requirement after rising at eight and eating steel-cut oats with kale and fruit and yogurt, before a day of buying, managing, designing, hiring, firing, tasting, making bitters and otherwise performing the endless front-of-house jobs required to run a successful principality of distinctive downtown bars and restaurants. She seems calmer and more yielding at this time of day, but not that much more yielding.

"I'm a little controlling," Jen Agg says. It's Monday. Yesterday she saw her beloved father, her biggest fan, "the only man I have never eye-rolled." He was a hard-working poor kid who became a teacher but preferred to flip houses and make money, who helped finance Cobalt, her first bar.

He has Alzheimer's now, which crushes her. On Sundays, she drives out to the house in Scarborough where she grew up and he still lives, to cook him a meal. (She is by her own admission "an amazing cook," though she has never wanted to slave in a kitchen for a living: It's not brainy or conceptual enough. "The restaurant business is not a business overflowing with intellectuals," she says. "That's not to say there aren't any smart people. But it's a different world.")

Lately she has been making her dad spaghetti, but plans to switch to penne soon: He can no longer manage the twirling of his fork. It's one of those details she is always noticing, that makes her good at what she does.

"He just says the same thing over and over again," she says. "And also, he forgets that I have success. Which is heartbreaking."