Make Ahead Mashed Potato Casserole. Remove the top and bake for 25 minutes. This casserole can be prepared up to two days ahead of time.
Boil peeled potatoes until tender. Step 1 Grease a 9x13-inch baking pan. Assemble the casserole as noted in the recipe but hold off on baking and refrigerate ready to serve.
Boil in large pot of salted water until tender.
Boil peeled potatoes until tender. Step 2 Mix sour cream Cheddar cheese and condensed soup together in a very large bowl. This casserole can be prepared up to two days ahead of time. Bring to a boil over medium-high heat reduce the heat to medium-low and simmer until the potatoes are tender when pierced with a knife about 15 minutes.