Simply sprinkle the assembled dish with grated cheese and bread crumbs moistened with a little melted butter and dried herbs if desired and continue baking until filling is cooked and topping is melted and bubbling. When you don't have the specific casserole baking dish called for in a recipe, it's best to think big. Opt to use a pan of equal or slightly greater volume. However, if you substitute a pan that is shallower than the one specified, reduce the baking time by 25 percent, if the pan is deeper increase the baking time by 25 percent. Measure water and pour it in the pan to check.
Casseroles really taste best when made in advance.
Time will allow the flavors to blossom. Once the casserole is frozen, use the excess foil overhang and seal airtight. Double wrap the foil wrapped casserole in freezer proof plastic bags, label, date it, then freeze until ready to use. To thaw, remove the wrapping and place the frozen food back into the dish in which it was assembled or baked. Defrost and reheat or bake as recipe instructs.