Since I have to search this recipe every year, I'm putting it here..
Courtesy of Freckled
5 pounds Yukon gold or other kind
2 (3 oz) packages of cream cheese
8 oz sour cream
1/2 c milk
2 teaspoons onion salt
black pepper to taste
Ok so boil potatoes like usual and mash. Then put the other stuff in and mix it up. Put in casserole dish and you can reheat it the next day at 325 for 50 minutes or so.
The whole point of the recipe is so you can do it beforehand. Works well!