In a lighlty greased 2-quart casserole dish, place a layer of mashed potatoes; then arrange sausages in a sunburst design. Sprinkle with salt, pepper, garlic powder and onions to taste. Place sliced VELVEETA on this, covering the sausages (4 to 6 slices). Repeat layers in this fashion until all ingredients are used. The last layer is topped with a generous amount of VELVEETA. Bake at 350°F for 25 to 30 minutes. Finish up with broiler if VELVEETA is not browned. Makes 4 to 6 servings.