Outside of restaurants, though, the bread could be hard to come by. So at the end of last year, I was delighted to discover a small storefront selling all the familiar Sullivan St breads and two cookies that, like everything Sullivan St makes, are exemplary: biscotti pratesi (almost as good as mine) and ossi di morti, shatter-light meringues with almonds. The location, at 72nd Street and Broadway, was convenient to my brother’s apartment, where I stay, and perfect for buying and packing a loaf of the incomparable sesame bread—not just scattered with but rolled in a dense bed of sesame seeds—just before going to the airport. The name was unfamiliar: Grandaisy, with a pretty pale-blue daisy logo on the bags. The clerks reassured me that indeed, the bread was the same.

Sort of. When I recently ran into Lahey, a longtime acquaintance and an inexhaustible source of pungent, often profanity-strewn, quotes, I told him how happy I was finally to be able to buy Sullivan St breads every time I came to New York. “Those aren’t Sullivan St breads,” he said drily. Whaat?

The explanation, I learned when I went to see Lahey at his new Sullivan St Bakery headquarters in the far-west reaches of Hell’s Kitchen, was a romantic breakup that devolved into a rocky professional partnership that ended in a complete business split. Now there were two bakeries with two different names selling breads and cookies identically named and to all appearances utterly identical, one owned by Lahey and the other by his former partner, Monica Von Thun Calderón. Talk about confusion in the marketplace! I was certainly confused. I wondered how the Siamese twins had been parted, and how the twin breads would taste when reunited and compared.

I was put in mind of a much better-known baking breakup, which coincidentally has put two more bakeries on the Upper West Side selling very similar products: that of the two founders of Magnolia Bakery, which shot to fame after its way-too-cute cupcakes provided consolation to the women on Sex and the City. The television exposure started a cupcake craze in which tourists make pilgrimages to the West Village original (it’s a wonder there aren’t Japanese tourists dressed as cupcakes, or at least as Samantha). In a non-cute spat that delighted tabloids, the two women parted ways, and one of them opened a rival bakery called Buttercup Bake Shop. The owner of Buttercup (Magnolia has changed hands) did not want to talk to me about the split. But I noted with interest that when I asked for Magnolia Bakery on a call to 800-GOOG411, the free voice-activated directory-assistance service, the first listing I got was for Buttercup. (Maybe Google really is omniscient: Buttercup is the much better baker.)

However entertainingly operatic, the details of the Sullivan St separation are too complicated to go into here, and subject to the same side-choosing as in any divorce. A side story of skulduggery is more dramatic still, if potentially litigious: as Lahey tells it, a former distributor of Sullivan St breads hired former Sullivan St bakers to start his own bakery, opened suddenly with an extremely similar product line, and started making deliveries to Sullivan St customers with no notice of a change of vendor—initially in stockpiled bags with the Sullivan St name and logo, yet. “It was almost the perfect crime!” Lahey says Mario Batali called out to him one day, getting off his Vespa. (A lawsuit Lahey brought against the distributor over money he was owed was settled out of court.) The threat to their business galvanized Lahey and Von Thun Calderón to join in battle, and within a year they had won back many of their lost customers. But after weathering the crisis, the sparring partners split for good two years ago.