1. Open the scallops, clean and prepare. Slice the white flesh and saute gently, with the corals, in the butter for 2 minutes, then add the wine and continue to cook for a further 3 or 4 minutes.
2. Remove the scallops with a slotted spoon, separate the corals and reserve with the white flesh, and keep warm on a heated plate.
3. Bone the flounder for stuffing or ask your fishmonger to do this.
4. Into the warmed Bechamel Sauce, stir in 3 to 4 tablespoons of stock from the scallops, and mix in the prawns and white flesh of the scallops.
5. Season with salt and pepper to taste. Stuff this mixture into the cavities of the flounder, arrange on a lightly buttered baking dish and squeeze a little lemon juice all over and dot with butter.
6. Bake in a moderate oven (180c, 350f, gas 4) for about 20 minutes, until tender.
7. When the fish is cooked, serve on four warmed plates and garnish with the scallop corals, and sprigs of chervil or parsley.