Pro Tips: Slice potatoes thinly and evenly (about ⅛-inch) for even cooking. Pour beef broth around the edges to keep potatoes moist. Cover with foil for the first 30 minutes to trap moisture. Let the casserole rest for 5 minutes before serving to help it set. Add extra veggies like bell peppers or mushrooms for more nutrition. This casserole freezes beautifully for up to 3 months.