In large skillet simmer scallops over low heat in broth, wine, and lemon juice. Cook 2 to 3 minutes, just until scallops become opaque. Do not overcook. Drain, reserving cooking liquid.
Sauté mushrooms and scallions in 2 tablespoons butter over medium heat 3 to 5 minutes. Remove from pan. Stir flour into pan. Stir in reserved cooking liquid, parsley, cheese, and seasonings. Cook, stirring continuously, until sauce is smooth and thickened. Add scallops and mushrooms. Cook 1 minute until reheated. Serve immediately.
If desired, spoon mixture into individual baking shells. Sprinkle with seasoned breadcrumbs. Dot with butter. Brown slightly under broiler. Serve immediately.