Grain Store, Granary Square, 1-3 Stable Street, London

It wasn't meant to be Grain Store this week. Trying restaurants when the paint's barely dry is tempting – like seeing a film on the first night, you want to be the one to air opinions before everyone's become bored by the whole subject. It's not helpful for chefs, restaurateurs or readers, frankly, since often things need tweaking and settling. But a set of circumstances bring me to Grain Store in its first few days. Happily, its chef/patron is Bruno Loubet, who's had enough launches to hit the ground running, and who has a clever idea to show off.

The restaurant is in a new development of an old building behind the unlovely King's Cross station. The granary building is a slab of thing, prettified for 2013 with a geometric silver slash of paint all across it – as if Ziggy Stardust was Ziggy Stardust & Son, wholesalers to the vegetable trade.

In a cavernous corner space sits Grain Store. Full-height windows and high ceilings add air and atmosphere; if you're not sitting near a window – which most won't be – it could turn a bit genuinely cavey. An open kitchen at the centre and a bar help break up the space. And there, working the Josper grill, is Bruno.

He already runs the rather terrific Bistrot Bruno Loubet at the Zetter hotel in nearby Clerkenwell. This operation is several times the size and with a very different menu; Grain Store is all about the vegetables.

It's not a vegetarian restaurant, good God no! Loubet is French, and his daubes and boudins are something to behold. But Grain Store puts the veggies front and centre. Rather refreshing coming, as we are, off a seemingly endless cycle of burger and BBQ joints. The menus – printed on earthy colours – celebrate such produce as asparagus, cauliflower, potatoes and beetroot. It might be earthy, but it's not muddy. There are some brilliant combinations, and where an animal is involved in a dish, it comes at the end of the description, not the beginning. Just in case you were in any doubt.

Mr M has baked beetroot with pickled onions, goat labneh and a dill oil dressing (£6), followed by a corn and quinoa tamale with salsa and sticky pork belly (£15). I have seared asparagus with a green gazpacho sauce and rosemary and pink peppercorn Melba toast (£6.50), then braised endive, pickled radish, artichoke and pigeon, with popcorn (£15). For good measure, we share some broad bean, courgette and prawn falafels (£6.50).

There are some joyous-sounding cocktails on a menu devised by the masterful Tony Conigliari, from which a Death in Venice (Campari, prosecco and bits and bobs) is the least adventurous. Maybe next time I'll try a pumpkin and maple-syrup bellini… A good wine list includes "Tony's Greco Roman Wines", which are smoked or herb infused.

Largely served on plain white oval plates, each dish is a picture. The beets and pickles with a soothing goat-y yoghurt are bliss, the asparagus still the star despite dabs of silky sauce. The falafels come with a punchy, chunky raita.

The place is full to bursting and the staff, only at full speed for a few days, do well to keep things motoring. Our fantastic, pink-haired waitress Jenni keeps a watchful eye and when the mains are a little slow, she gets the kitchen to hop to it.

The tamale and pork belly is a study in calm. But once the corn is unwrapped, it scatters its wonderfully seasoned, crisp and nutty contents to mingle with the super-soft pillow of pork. My meat is off the Josper, pink within and juicy (one tiny niggle, the pigeon might have been trimmed a smidgeon better). The artichoke mousse is served in an eggshell with a wooden spoon. Affected? Maybe just a tad, but it tastes rich and grassy.

Of the puds, the spiced candied tomatoes with goats' milk pannacotta is a sensation. They are indeed fruits – jammy and sweet. A white-chocolate rice crispy with dark-chocolate mousse and almond ice-cream is, frankly, just rude (I ate it all).

I cannot wait to come back and romance my inner vegetarian. Grain Store is a triumph of a great chef thinking about what the London scene needs, and delivering it.

8/10

Grain Store, Granary Square, 1-3 stable street, London N1, Tel: 020 7324 4466. £80 for two, including two cocktails

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