The original version of this cheesy potato casserole stars canned soup, full-fat sour cream, a stick of butter and a crust of crushed potato chips. We lightened it considerably by using a homemade white sauce instead of canned soup and swapping nonfat Greek yogurt for the sour cream. Crushed corn flakes replace the potato chips. All in all, we slashed 200 calories, 25 grams of fat (12 grams saturated) and 170 milligrams of sodium per serving. Dig in!