The steak is perfect – or closer to perfect than any beef that has emerged from my kitchen before. Juicy, full of flavour, salmon-pink inside and as meltingly tender as a Mills & Boon kiss. My father, a proper red beef man, is full of admiration: he can't believe it's not fillet. But it was an ordinary piece of sirloin and pretty stringy when I started cooking it eight hours ago.

That's right. At midday, I seasoned four steaks and then vacuum-packed them. I put the bags in a SousVide Supreme water bath at 56C and let them stew until dinnertime. When they came out – limp and a bit beige – I seared them for a few seconds in hot oil. And was amazed.

We also ate vacuum-packed water-bathed broccoli – one hour at 83C – with the steak. This was even more of an eyebrow raiser. In fact, so gloriously broccoli-tasting was it that my children, who quite like the stuff when steamed for 10 minutes, wouldn't eat it. "Disgusting!" they said. "It's too strong!"

Beyond professionals and the trainspotters of the food blogs, vacuum-pack slow cooking is astonishingly little known. "Oh, yes, I love her work," a foodie neighbour said when I told him I was "cooking sous-vide tonight". Yet the technique, first used in France in the 70s, is now commonplace in professional kitchens from Little Chef to Raymond Blanc's. Poor Gordon Ramsay – not a phrase that comes easily – was unjustly turned over on the front page of the Sun last year for using "boil-in-the-bag" in his gastropubs. What the paper was exposing was, of course, pre-prepared sous-vide meals.

The key difference is that the bag doesn't boil. The technique uses science that isolates the temperature at which items you don't want in a finished food – fibres, tendons, connective tissue – break down. Then you cook at precisely that temperature. Because the food is sealed, nothing in it – flavour, nutrients, sugars, colour - goes AWOL. The results are spectacular, consistent and, in a busy kitchen, incredibly useful. "It's an extra pair of hands," says Anthony Worrall Thompson, who cooks steaks sous-vide for 12 hours to achieve maximum tenderness.

Sous-vide's failure to penetrate the home kitchen is in part because of expense – even the Supreme I have borrowed, which is the first water-bath pitched at the domestic cook, will cost £499. You need a good vacuum-sealer too: they cost at least £50, and are available from a variety of online gadget shops. There are also cultural problems. Too many of us have bad memories of Findus cod with parsley sauce to embrace cooking in plastic pouches.

Heston Blumenthal has used sous-vide since the mid-90s. Its arrival, he tells me, was "the biggest single change in the professional kitchen in the last 50 years – probably the last century." He has used a whirlpool bath to cook an entire vacuum-packed pig, but it is simple dishes such as fresh fish that he believes are most easily rewarding. "You can vacuum-pack a piece of red or grey mullet with a little fennel and lemon, put a sticker on it saying what temperature and time in the bath it needs, and that's it." You are guaranteed fish that has all its flavour and juices, "better than most restaurants can cook it". Blumenthal is currently working with a manufacturer on a sous-vide system for home cooks next year – vacuum sealer and bath will retail for less than £300, he says.

I try his sous-vide scrambled eggs; "never in my life have I eaten eggs so perfectly cooked," says a blogger who attended demonstrations Blumenthal did in the US last year. You put three eggs in the pouch, add 20% of their weight in butter and cream and cook at 73.2C for 50 minutes, just above the temperature at which the proteins begin to coagulate. This wasn't easy. How do you vacuum-seal a liquid? I kept sucking the egg whites into the machine along with the air. Then, when cooking starts, you have to take the pouch out of the bath and massage it every few minutes. Eventually – a dozen eggs later – I worked it out. The scramble, just clotted, was gorgeously eggy and unctuous.

Most hi-tech equipment that reaches the domestic kitchen is, like the microwave, designed not to improve food, but to simplify cooking or lower costs. The sous-vide is something else – a leap forward in the evolution of cooking. We should be excited.