Drain and mash potatoes with sour cream, cream cheese, 1 cup butter and half and half; reserving 2 tablespoons of half and half.
Add onions and salt and pepper to taste.
Spread potato mixture into 9” x 13” baking dish. Cover entire surface with cheese slices. (Dish can be prepared to this point and refrigerated overnight.)
Preheat oven to 350°. Float remaining half and half on top and sprinkle with sugar. Bake 35—60 minutes until heated through.