Green Bean Casserole Ingredients Topping: 2 slices high-quality white sandwich bread, torn into pieces 2 Tablespoons unsalted butter, melted ¼ teaspoon salt 2 cups canned fried onions Casserole: 3 Tablespoons unsalted butter 10 ounces white mushrooms, sliced thin 1 teaspoon salt ½ teaspoon pepper 6 garlic cloves, minced ½ teaspoons dried thyme ¼ cup unbleached