Open on lively fire 1 kg of mussels. Remove shells, filter the juice. Poach 6 - 7 minutes 8 whole scallops in half liter of dry white wine with salt and pepper. Drain scallops, reserve the liquid of cooking.
Make a "roux blond" with 1 tablespoon of flour and 50 g of butter, dilute bit by bit with the cookingjuice of shells and that of the mussels. Thicken on slow fire 10 minutes.
Add 2 tablespoons of crème fraiche, lemon, season to taste. In 4 hollow shells, distribute mushrooms, mussels and flesh scallops. Coat with the sauce, sprinkle on bread-crumbs, put a pat of butter on top. Place under the grill until golden brown.