The annual Edinburgh Festival, which started last weekend, brings a lot of things to the Scottish capital. Naked mime artists, burp opera - even, if you're lucky, some comedy. Far more entertaining for the city's bars, pubs and restaurants, however, are the incoming tourists, who for two weeks every year put on their very own spending festival.

For Alex Thain, the 26-year-old head chef of Cosmo, this has already meant a group of 32 American tourists - ching! ching! - who booked the entire restaurant last week. For that, he has Gordon Ramsay to thank, as he pointed one of the party (a regular at his London restaurants) in the direction of Thain after the young Scottish chef won the Gordon Ramsay Scholar competition last September.

Fired up
Indeed, September was a whirlwind time for Thain. He had been approached when sous chef at Conran's Glasgow restaurant Etain by Cosmo's owner Keith Murray (son of metals magnate and Glasgow Rangers FC chairman David) to bring a new direction to the restaurant. Just five days after starting, he travelled to London for the Ramsay final, which he won. "It was a busy time," he says, "but I came back fired up, thinking, 'Right, now I've got the title, I definitely have to change the menu.'"

Cosmo was established in 1969 as an Italian restaurant and continued to serve smart, but dated, Italian cuisine even after the Murrays had taken it over. Thain, however, has updated things to a more contemporary style of fine dining, but one that values simplicity over elaborate assemblies and puts an emphasis on the best local Scottish produce. Lamb comes with provençal vegetables, therefore, while beef fillet is served, classically, with girolles and Madeira jus.

In fact, Thain says his "most modern dish" is the halibut main (£21.50), thanks to the orange foam which tops it. He caramelises langoustines, mixes them with crushed new potatoes and aïoli, then places a steamed halibut fillet on top, then fresh broad beans and clams. To finish, he makes an orange oil by heating the zest of orange in olive oil to about 65°C for 2-3 hours.

He adds: "With that oil, I make an orange mayonnaise, put it in the espuma gun, heat it to 55°C and foam it over the clams." For a final intense orange note, he sprinkles over bits of dried orange zest.

The rest of the menu, Thain says, is pretty simple, but there are plenty of bold flavours, particularly with fruit and fish. "Citrus fruits go really well with fish, particularly grapefruit with crab," he says. A starter of crab tian with pieces of lobster, avocado guacamole and a pea shoot salad duly has chopped segments of grapefruit in it. "Lemon can be too harsh and kills the flavour, while orange is not enough," he says.

Lighter dishes
Pan-roasted turbot with herb and ricotta gnocchi (£23), meanwhile, comes with a quenelle of scallop, tarragon and pineapple tartare, made by mixing tarragon with scallop, pineapple and ginger brunoise.

The lunch menu (£17.50 for two courses, £21.50 for three) features lighter dishes and simplified variations of dishes from the evening à la carte, to keep food costs down. So the crab tian loses its lobster and is served with a Charentais melon soup, while a sea trout main swaps crab risotto for an orange, fennel and tomato salad.

The lunch menu changes every two or three weeks, while the evening selection changes every three months according to the seasons. Thain also offers a tasting menu at £48 for seven courses (plus an extra amuse-bouche and pre-dessert), which so has so far been well received. "On Saturday nights we often have about three-quarters of the restaurant ordering it," he says.

Customer numbers for the 45-seat restaurant have been about 20 at lunch, going up to 30 and often 40 in the evenings. With five chefs working in the kitchen, and no designated pastry chef, this is a manageable number.

The clientele has been both businessmen and shoppers from the nearby boutiques on George Street, a mix Thain is keen to encourage. "We want to aim at the top end but we don't want to be exclusive," he says. "I'm happy to have anyone here, even Joe Bloggs wearing jeans and a T-shirt."

Anyone - though, we presume, not the naked mime artists.

What's on the menu

• Wild salmon gravadlax, home-made lemonade and horseradish sauce, £10.50
• Salad of sautéd foie gras, pickled rhubarb, hazelnuts and balsamic vinegar, £14
• Ballotine of smoked ham hough, home-made piccalilli, sourdough toasts and black pepper, £11
• Roast rump of spring lamb with confit shoulder, provençal vegetables and sage jus, £22
• Scotch beef fillet, oxtail ravioli, girolles, mushrooms and Madeira jus, £25
• Pan-fried sea trout, crab risotto, crushed peas and pea velouté, £21.50
• White chocolate panna cotta, roasted apricots, Champagne sorbet and granité, £7.50
• Salted peanut parfait, cherry jam, milk mousse and peanut brittle, £7.50
• Mascarpone semifreddo, poached strawberries and strawberry sorbet, £7.50

Cosmo, 58a North Castle Street, Edinburgh EH2 3LU.
Tel: 0131-226 6743. Website: www.cosmo-restaurant.co.uk

See a map of Cosmo here >>