2 tbsp. vegetable oil
1 c. chopped onion
2 1/2 c. cooked potatoes
3 eggs
1/2 c. heavy cream
1/4 c. butter
1/4 c. grated Parmesan

Preheat oven to 350 degrees. Grease 1 1/2 quart casserole; set aside. In small skillet heat oil over medium heat. Add onion and cook, stirring occasionally 5 minutes or until soft. Place onions, potatoes, eggs, cream, butter and Parmesan cheese in blender or food processor. Cover, process until smooth. Pour mixture into casserole and bake 1 hour.