In a saucepan, place scallops in water to just cover, add lemon and parsley, bring to a boil and boil 2 minutes. Drain, reserving liquid and removing scallops to a plate.
In a small skillet, sauté scallions and mushrooms in 2 Tbs butter 2-3 minutes, stirring often.
Melt 3 Tbs butter in the saucepan and stir in flour to blend. Gradually add the reserved scallops liquid, plus worcestershire, salt and pepper to taste, stirring continuously until smooth and thickened.
Remove from heat and stir in sherry. Add scallops and onion-mushroom mixture.
Turn into a greased baking dish; sprinkle with bread crumbs and parmesan cheese.