Remove and chop mushroom stems; set the mushroom caps aside.
Melt 3 tablespoons of butter in a large skillet add the chopped mushroom stems, onion, and garlic. Sauté 3 to 5 minutes or until tender. Stir in bread crumbs and next 7 ingredients until mixture is well blended. Gently stir in crabmeat.
Spoon crabmeat mixture evenly into mushroom caps. Place on rack in a broiler pan. Drizzle with melted butter.