In a nutshell: Elystan Street's founder and head chef Phil Howard got famous at 24, when he hit the ground running as head chef at luxury restaurant The Square in Mayfair. Working 19 hour days, Howard's formula (classic food, serve in suave new ways), was remarkably successful and became renowned.

A turn toward the party lifestyle was a temporary downfall - but twenty years on, Howard is back to setting up world-leading kitchens in London. His latest is game-changing new restaurant Elystan Street.

The welcome: The restaurant is halfway down a beautiful and very well behaved residential street in South Kensington. So discreet, you'd have to know about it to ever wander this way. There's a formal feel to the meeting and greeting, where the first things you'll notice are a private dining alcove and poised receptionists; but as you sit down the service becomes conversational and relaxed, matched by open-collared service so friendly it almost feels at odds with the alarmingly steep prices. When the cheapest main is £30, shouldn't we sit up straight?

The space: Given that Elystan Street's charm offensive has made it talk of the town, it's surprising that the design work by Clare Nelson Design feels distinctly unlike a restaurant. Essentially a rectangular hall, it is unclear what was here before but some serious internal wall removal must have taken place.

It is unusual, but likeable and breezy with Nordic minimalism at every turn (from swept-back chairs to the floors, flanked in light wood). The room feels more like a dance hall than eatery - there is no good or bad table - but the wide open spaces throw around the room's live debate for all to hear.

Food and drink: The menu changes almost daily, and little alterations reflect the seasons. Open for lunch and dinner, the a La carte - with wine included - will cost around £80 a head for three courses. It's expensive even for South Kensington. But there's the feel that the food really is worth getting dressed up for, and probably best saved for a special occasion. And judging from the sellout restaurant the Tuesday we went, people are celebrating special occasions whenever Elystan Street can possibly fit them in.

From a contemporary menu that makes the most of truly special pairings, we began with a tartare of aged beef on a bed on artichoke heart, truffle, beetroot and horseradish. A waiter with a refreshingly unpretentious and gentle approach found a delicious white to pair with the artichoke, and the beef had a sumptuous creaminess lent by the horseradish sauce. Piled atop the sliced artichoke, it's a delicate dish (and an Instagram moment), abundant with flavour.

The main plates are generally rich, and tremendously exciting. Even for the two vegetarian options, there's no avoiding truffle, hazelnut, nut milk and mushroom puree. We ate the plume and cheek of pata negra pork with caramelised endive and sweet and sour grapefruit, where the star of the show was the tangy grapefruit compote, a gorgeous rich orange which bolstered the two lean cuts of pork when used sparingly to counteract. Our guest had the breast of mallard with pumpkin and chestnuts and a pie of the leg, with crab apple. Telling stories with dishes, the duck leg pie was all we could talk about, delicately handmade and positioned on the plate next to a pool of fresh pumpkin to act like the grapefruit in the former dish: a sweeter sidekick to the rich decadence.

Desserts flowed too, and were more obviously obeying Howard's mantra of carefree indulgence. The smashed brownie came with everything but the kitchen sink thrown at it: hazelnut ice cream and vanilla cream where the two ingredients listed, though the whole thing fizzed and popped on the plate and required chewing with childlike abandon and ferocity. We couldn't see much point to the chocolate foam, though, on top of an already chococolatey - and not very delicate - abyss. Unusual pairings made the ice creams divine (particular favourites, the burnt honey and bay and pear) and other delights (you have to eat dessert) included poached pairs with sorbet and creme fraiche and figs with goat's milk ice cream.

Would we return? Howard's party line about eating indulgently makes this a celebration spot to savour, rather than make a weekly favourite. Prices are alarmingly high too, so much so that repeat visits wouldn't be as much fun if they were made common. So go irregularly, and Elystan Street'll be your new best treat.