This sounds like a weird combination of ingredients, but it's really good. I adapted this from a higher-fat recipe I found on the internet. It's still not low fat, but at least better for you than the original. Delicious left over too! Leftovers can be put into a baked potato for another main dish meal, or stir cooked rice and smoked sausage or cooked chicken or ham into it and re-bake it for another casserole. It freezes well for use later on in a potato, or as a soup if you puree it. You can use real mayo, miracle whip, or the store brand equivalent. Also velveeta (4-6 ounces) works as well as cheddar. 18 saltines is about 1/2 a sleeve of saltines from the box. You don't have to really measure them exactly. You can also use other crackers that you have such as cheese-its, or ritz types that are a little stale.