Potato Puff

Potato Puff
1 onion, finely chopped
3 cloves garlic, minced
1/4 cup butter
3 cups mashed potatoes
1/3 cup sour cream
2 tablespoons Dijon or yellow mustard
1/2 cup milk
1/2 tsp salt
1/8 tsp white pepper
2 eggs, separated
1-1/2 cups shredded Cheddar cheese
2 tbs grated Parmesan cheese
Preheat oven to 350 degrees F. In small skillet, cook onion and garlic in butter until softened, about 6-7 minutes.

Place mashed potatoes in large bowl and beat in onion mixture. Then add sour cream, mustard, milk, salt, pepper, and thyme and mix well. Beat in egg yolks.
In small bowl, beat egg whites until stiff peaks form. Fold into potato mixture along with Cheddar cheese.Pour into greased 2-quart baking dish. Top with Parmesan cheese. Bake for 45-50 minutes until the mixture is puffed and light golden brown. Serve immediately. Serves 4-6