Make ahead of time. This bake can be prepared through step 4 and frozen; store the topping separately and add it once the bake is thawed. It can also be frozen after baking. Wrap the dish with plastic wrap, then aluminum foil, and store for up to 2 months in the freezer. When you are ready to eat it, thaw it overnight in the fridge. Remove all the wrapping and bake at 350°F. If it had been prebaked, bake for 20 minutes; if not, bake according to the recipe directions above.
o For a more savory casserole, add ham and cheese, chorizo, green chilies, sausage, or crumbled bacon.
o For a sweet casserole, add thinly sliced apple, orange zest, sliced apricots, sliced pineapple, blueberries, or chopped pecans.