Baked Potato Casserole Recipe. This classic comfort food side dish is also known as smashed potato casserole or sour cream potatoes. No matter what you call it, it's INCREDIBLE and absolutely DELICIOUS. This oven baked treat would be excellent to add to a list of unique ideas for your next Thanksgiving or Christmas side dish. You'll need potatoes, sour cream (or greek yogurt), milk, sharp cheddar cheese, shallots, and parmesan cheese.