Make white sauce by melting butter, add flour and cook until it bubbles, add onions, simmer a minute. Add hot milk and cook until sauce thickens. Add peeled raw shrimp, pimentos and liquid from one whole can, 2 tablespoons Lea and Perrins sauce and beef bouillon cubes disolved in hot water, dry mustard, chopped onion tops, dash of tabasco sauce. Before removing from fire, add beaten egg and cream. Mushrooms optional.