Rinse and drain mushrooms. Remove stems. reserve caps. Chop enough stems to make 1 cup.
In medium saucepan cook the chopped stems, onions and garlic in butter unil tender. Stir in breadcrumbs and cheese. Spoon crumb mixture into mushroom caps. Arrange mushrooms in a baking pan.
Bake in a 425 degree oven for 8-20 min or until tender.
