Philip's side of the family in Michigan make this for holidays and he LOVES it (and asked me to get the recipe). Here it is:
One 2 lb bag frozen hash browns partially thawed
1 pint sour cream
small onion minced
3 cups of shredded extra sharp cheddar cheese
2 cans cream of potato soup (I actually prefer Cream of Chicken in this)
Mix all ingredients together. Put in lightly greased 9 X 13 pan and sprinkle top with grated parmesan cheese. Cover with foil and bake 1 1/2 hours at 325 degrees. I usually take the foil off for the last 10 - 15 minutes to let it brown.