1/4 cup butter or margarine
1 tablespoon minced onion
2 tablespoons all-purpose flour
1 (4 ounce) can sliced mushrooms, drained
1/4 cup white wine
1/2 teaspoon salt
1/8 teaspoon ground black pepper
1 pound bay scallops
1 bay leaf
2 teaspoons lemon juice
1/2 cup milk, light cream, or evaporated milk
1 egg yolk
1 tablespoon chopped fresh parsley
Combine butter and onion in a 2-quart, microwave-safe casserole. Cover, and microwave on High for 2 minutes. Stir in flour until well blended, then stir in mushrooms, wine, salt, pepper, scallops, bay leaf, and lemon juice. Recover, and microwave on High for 6 minutes, or until the scallops turn opaque. Remove and discard the bay leaf.
In a small bowl, stir together the milk and egg yolk until combined. Stir the hot liquid from the scallops, about 1 tablespoon at a time into the milk mixture. When combined, stir the sauce back into the scallops.
Cover, and microwave on High for 2 minutes, then stir, and microwave for another 3 minutes. Sprinkle with parsley before serving.