For Freezing. Leftovers: Let the casserole cool, and transfer into freezer-friendly airtight containers. Freeze for up to 2-3 months and thaw overnight in the fridge. Bake until warmed through. Individual portions can be reheated in the microwave. To make ahead and freeze: follow the recipe until baking instructions, cover with foil or plastic wrap, and freeze for 2-3 months. Thaw overnight in the fridge. Bake as directed.