For this elegant dish, wine-poached scallops and prawns are mixed with a light, low-fat cheese sauce, dusted with bread crumbs, and broiled in scallop shells until brown and bubbly. Equally appropriate as a first course or light luncheon, it has great nutritional benefits: plenty of calcium and good-quality protein are contained in both the shellfish and the sauce. A special bonus of this recipe is that can be made ahead and frozen for several weeks. Broil right before serving.
Wash scallop shells and place on a cookie sheet. Preheat broiler.
Peel and devein prawns, then coarsely chop. Quarter bay scallops. In a medium saucepan over medium-high heat, combine shellfish and wine and heat until bubbling. Cook until scallops are opaque (about 1 minute), stirring constantly. Drain and reserve cooking wine. Set scallops and prawns aside.
In the same pan, heat butter over medium heat and sauteed mushrooms until they begin to exude moisture. If mixture gets too dry and begins to stick, add a small amount of reserved cooking wine. Stir in flour and cook for 2 minutes.
Add milk in a thin stream, stirring constantly with a whisk. Sauce should thicken immediately. If it doesn't, continue to cook over medium heat, stirring, until it is the consistency of heavy cream. Add Parmesan, scallops, and prawns, and remove from heat.
Spoon an equal amount of seafood mixture into each scallop shell. Top with bread crumbs and broil until lightly browned and bubbling (3 to 5 minutes). Serve hot (see Note).
For easier service, fold a linen napkin under scallop shells to keep them from tipping on the plate.