Last time I looked, Bath was pretty disappointing when it came to recommendable restaurants. It also suffered an inexplicable dearth of off-licences, and the people in the street were all wearing beanie hats. A year later, there's a new off-licence called Independent Spirit, specialising in posh malt whiskies, and the locals in the street are now all wearing BacoFoil shawls (I found out later they'd been running a marathon and were equilibrating their body-heat) – and there are now three brasseries to choose from – Bill's, The Tramshed (no relation of Mark Hix's chicken-or-steak joint) and Brasserie Blanc. But the happiest surprise is that when the Abbey Hotel changed hands last summer, the new owner installed Chris Staines to run the restaurant, which is re-named Allium, the genus which contains onions, leeks and garlic.

Staines is a top choice: he was Chef de Cuisine at Marco Pierre White's Oak Room, then head chef at Foliage, the fine-dining bit of the Mandarin Oriental in Knightsbridge where I can still remember, years ago, eating raw tuna with crab slathered with wasabi ice-cream and, get this, crunchy flying fish roe. Staines likes to give his diners little surprises. So I took three friends there with anticipation.

The Abbey Hotel isn't a glamorous venue; the bar is small and spasmodically staffed, and the restaurant remains as bland as before – the tables formica, the chairs an inoffensive lavender – although the decorators have added some would-be-edgy art (Warhol's Marilyn Monroe, a couple of sub-Jackson Pollocks) and two gigantic neo-Etruscan pots standing in alcoves. No matter. The menu holds the attention from the start, with its eccentric line-up of co-star ingredients.

Take the miso-cured Loch Duart salmon: the softest salmon that's ever touched your lips, it came with a hundreds-and-thousands shower of seasoning, plus a fried oyster fritter for spiky contrast. Also featured was pickled cucumber, grapefruit and a smear of wasabi dressing – a stunning mini-banquet of zingy flavours. Butternut squash soup with sage pesto tortellini and a wand of crispy prosciutto was accompanied by a millefeuille-sized Welsh rarebit. It was, said Marilyn, "velvety and piquant, very comforting".

Quail glazed in chilli caramel was irresistible, but there was more to it than chilli and caramel – how about random additions of Chinese cabbage, roundels of palm hearts, lychee, peanuts and coriander? "I'm surprised by the peanuts," said James. "They're too assertive. But the quail's fine and the salad items cool down the chilli." I found the glaze on the quail too close to teriyaki sauce, but the spices left my tastebuds buzzing like hornets. Aminatta's salad of salt-baked beetroot looked a treat, the white and red beetroot echoed in the ruby endive, even if the goat's cheese failed to deliver pungency.

The main courses promised more heterogeneous shenanigans. Poached fillet of Atlantic haddock was surrounded by tugboats of Cornish mussels and (excellent idea) chorizo with butternut squash – a very orange plateful, but intensely satisfying. Slow-cooked belly of pork was soft but al dente, given a blood-and-ashes kick by salty black pudding, the piggy earthiness of both balanced by crispy carrots and curly kale.

The nearest the chef got to everyday cooking was my breast of corn-fed chicken, with crushed Jerusalem artichokes, purple sprouting broccoli and truffle cream sauce. But what a plateful! Were I enough of a hipster to photograph my supper, I'd have Instagrammed it: a great tranche of chicken surrounded by lumps of artichoke, chicken thighs stuffed with duxelle mushrooms, pickled radish… It was welcomingly hearty and filling for a cold March night.

The only dish that disappointed was the sea bream. See if you can spot the odd man out in these ingredients: sea bream with sautéed potatoes, violet artichokes, octopus, salsa verde and lemon curd. That's right – lemon curd. "The fish is perfectly cooked," said James, "but there's too much of a fight between the artichoke, salsa verde and lemon curd. It's too noisy." I had to agree. The chef said he thought the fennel might cut through the sweetness of the lemon curd. Sorry, it didn't.

Puddings were mostly delicious. My lychee panna cotta was a dream of South Pacific sweetness, and lifted to the blue empyrean by a wonderful lemongrass granite. Muscovado sponge with mascarpone cream and a pear poached in brown sugar syrup was joy enough without the addition of caramelised hazelnuts and white coffee ice-cream. The meal ended as it began, with dishes that offered a slightly crazed generosity of textures and curlicues of flavouring. Not all of it worked, but I hope you get to experience Staines's liberality and boldness of ambition when you're next in the badlands of Bath. He's a chef in a million.

Allium, Best Western Abbey Hotel, North Parade, Bath, Somerset BA1 1LF (01225 805249). Around £140 for two with wine

Food ****

Ambience **

Service ****

Tipping policy

'No service charge. All tips go to the staff'

Side orders: Scrummy Somerset

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