Preheat oven to 375 degrees F.
Spread the mashed potatoes into a buttered 1 quart gratin
dish. If a flat effect is desired, cover the potatoes
with plastic wrap and press evenly flat with your hands. Then remove plastic wrap
, season with salt and pepper, to taste, and sprinkle with Parmesan.
Bake until top is golden and crispy, about 20 to 30 minutes. Serve with reheated leftover gravy