Celery is not usually thought of as a main ingredient, but this recipe is a surprisingly delicious exception. The casserole is an excellent way to use an abundance of celery, and it's a dish you'll make again and again. And did you know you could freeze celery? Granted, it will lose its crunch, but it will still be fine for soups, casseroles, and other cooked dishes. Freeze raw, blanched, or stir-fried celery in airtight containers. If you prefer to use a seasoned homemade sauce instead of soup, i've included a brief recipe in the tips and variations section. Or use a basic bechamel or variation. A little cheese in the sauce would be good as well.