Clean mushrooms. Set the Portabello caps aside. In a large frying pan or saute pan, saute the chopped mushrooms in butter and oil. Until softened, remove. Cook shrimp and scallops in oil and butter, with shallot.* Return the mushrooms to the pan. Combine the rest of the ingredients. Stuff into portabello cap and bake at 350? for about 15 min. *If using uncooked fish, cook at this time as well.