Place cleaned mushroom caps in large zip-top bag with salad dressing, garlic, and 2 teaspoons fines herbs. Seal bag and massage gently to combine ingredients. Marinate 30 minutes to 1 hour.
Preheat oven to 375 degree F. Lightly spray a baking sheet with olive oil cooking spray; set aside.
In a small bowl, combine remaining 1 teaspoon fines herbes, Parmesan, bread crumbs, and melted butter; set aside.
Remove mushroom caps from marinade and place on prepared baking sheet. Fill each cap with 1 to 2 tablespoons green bean casserole. Top with a heaping spoonful of bread crumb mixture. Roast in preheated oven for 15 to 18 minutes or until golden. Serve hot.