Put sausage, garlic, onions and olive oil in a heavy sauce pan. Cook on medium heat. Stir often and make sure sausage doesn't clump. When sausage is cooked, simmer for 15 minutes. Remove from heat, stir in Parmesan cheese and bread crumbs.
Preheat oven to 450F. Spoon stuffing into mushroom caps. Arrange in baking pan, sprinkle lightly with olive oil and paprika. Bake for 15 minutes.