3tablespoons of the white wine you have chosen for the meal
Open the scallops by sliding a small sharp knife between the top and bottom shells and carefully cutting through the muscle which holds the flat shell in place. Remove each scallop from the concave shell with a teaspoon and remove the spongy beard so that you have only the white ‘noix’ and the orange coral (if any) from which you should detach the black sac. Wash the scallops in several waters to remove every trace of sand, and dry carefully on a towel or kitchen paper. Throw out the trimmings and shells.
Trim and clean the leeks, cutting off the roots, taking off the outside layer and cutting off the green part. Split them in half lengthways. Wash very carefully under the tap, using tepid water to dissolve any mud more easily, and shake vigorously to drain them. Then cut into little narrow strips 3–4cm (1¼ – 1½inches) long, and put with 15g (½oz) of the butter and 4 tablespoons water in a small saucepan. Salt lightly, cover and cook for 20 minutes over a slow heat, stirring from time to time with a wooden spoon. Set on one side and keep hot.
Cut each scallop in two horizontally, leaving the corals whole. Melt the remaining butter with the chopped shallot in a small saucepan and add the scallops and their corals. Cover with the vermouth and white wine. Do not add salt. Bring to the boil and simmer for 2 minutes, then remove the scallops with a slotted spoon and keep hot with the leeks.
Return the saucepan in which the scallops have cooked to the heat, and allow to reduce briskly. Add the cooking juices from the leeks, and reduce until there is no more than 3–4tablespoons of liquid left. Then add the cream and bring briefly to the boil. Taste for seasoning and add salt and pepper if necessary, then strain the sauce over the scallops and leeks. Sprinkle sprigs of chervil over the top, divide between hot bowls or deep plates and serve immediately.