Preheat oven to 375 degrees. Wipe mushroom caps clean with a damp cloth. In a large skillet heat oil and 1 tablespoon butter over medium high heat. Add onions and cook for 1 minute. Stir in chopped mushroom stems and cook until soft, about 2 minutes. Stir in the garlic, bacon and fresh parsley. Toss to coat and cook for another minute. Remove from heat and add breadcrumbs a half cup at a time. Add just enough bread crumbs so that mixture remains moist. Season mixture with cayenne, salt and pepper. When mixture is cool enough to handle stuff the caps. Place the stuffed caps in a baking dish and drizzle with 2 tablespoons of melted butter. Bake for 12-15 minutes or until heated through. Serve immediately.