1 (10 oz) package frozen baby lima beans
1/3 cup chopped onion
1 tablespoon butter OR margarine
1 tablespoon flour
1/4 teaspoon dry mustard
dash pepper
1/3 cup milk
1 cup grated cheddar cheese, divided
1 (4 oz) can mushroom stems and pieces, drained
1/2 cup seasoned croutons

prepare limas as directed on package. place onion and butter in small bowl. microwave on HIGH 1-1 1/2 minutes, or until tender. stir in flour, seasonings and milk. microwave on HIGH 45 seconds-1 3/4 minutes, or until thickened, stirring once or twice. combine sauce, 3/4 cheese and mushrooms, stirring until cheese melts. add to limas. sprinkle with croutons and remaining cheese. microwave on HIGH, uncovered, 1 1/2-2 1/2 minutes, or until cheese melts.