Combine soup and sour cream in large mixing bowl.
Add in onion.
Add butter and cheese, cut into cubes
Then mix in frozen potaoes
Salt and pepper
Spread mixture into a buttered lasagna pan (a 9 x 13 pan works too, may need to cook longer)
Bake in preheated 350 degree oven for 1 hour. I usually stir about halfway through baking time.
If you are going to be serving on a buffet in a crock pot, reduce the cooking time by about 15 minutes so the potatoes don't get too thick.