Mayonnaise on its own will separate if frozen, but in combination with other foods freezes just fine. Similarly, a dish that has a large quantity of milk may also separate during thawing, but is likely to go back together when heated.
You can successfully freeze most casseroles. There are certain foods that do not take well to freezing - many kinds of potatoes get mealy, while rice and pasta tend to taste a bit stale. So you might want to prepare and freeze the main part of your casserole and add the starch when you’re getting it ready for the table. Foods containing pepper, onion, garlic, cloves, and curry powder undergo flavor changes during freezing, so it is best to season your casserole lightly before it goes into the freezer and jazz it up when you’re getting it ready. Sauces thickened with flour will separate when thawed. The use of cornstarch or instant tapioca will eliminate that problem.
Whether the entire dish is cooked beforehand or not, it is a good idea at least to blanch the vegetables before freezing them. This keeps them from becoming soggy and shapeless when you do cook the dish. If you cook the casserole first, don’t cook it thoroughly, otherwise it will be overdone when you’ve reheated it.
For safety’s sake, if you cook the dish first, it must be chilled before putting it in the freezer, and to slow the development of bacteria, it should be chilled quickly. One way is to put the dish in a sink of very cold water, where the water comes up nearly to the lip of the dish. If you add ice to the water, the process will be even faster. Then chill it in the refrigerator for a couple of hours before transferring it to the freezer. On the other end, thaw it in the refrigerator for a day or so - don’t thaw it at room temperature.
If you line your casserole or baking dish with heavy aluminum foil before assembling the recipe, once frozen, you can lift it out of the dish and have the dish available for other cooking projects while your casserole quietly stays wrapped in foil in the freezer.
There are thousands of casserole recipes available online. Between those and your famous chicken lasagna, we’re sure you’ll have plenty of options to pack your freezer.