Preheat oven to 325. In large skillet, cook sausage over medium high heat, stirring frequently until thoroughly cooked and no longer pink. IN large mixing bowl, mix eggs, milk, mustard and salt; stir well. Distribute half the bread cubes evenly in buttered 13 x 9 inch baking dish. Sprinkle with half the pepper, half the cheese, half the sausage and half of each optional ingredient. Repeat layering using remaining bread cubes, pepper, cheese, sausage and optional ingredients. Pour egg mixture evenly over the casserole. Bake, uncovered, for 55 to 60 minutes or until eggs are set. Tent with foil if top begins to brown too quickly. Makes 6 servings.