I don’t know how Fake Cream of Greens Soup would work with different lettuce varieties but why not give it a try? I call this “Fake Cream of” because unless you use cream as the liquid, it’s not a high-fat soup; and “Cream of Greens” because it works with a wide variety of green veggies. It’s a good way to use up odds and ends which makes it appropriate for this post (I hope).
1. Saute chopped onions, and chopped carrot/celery/sweet pepper if you want.
2. Add cleaned, roughly chopped lettuce (don’t bother drying it) and a little water. Cover and steam till lettuce is cooked and soft.
3. Puree. I use a blender stick and puree only roughly. For a thoroughly smooth puree, cool the soup then puree in a blender.
4. Add liquid till you like the consistency. Liquid could be milk, cream, stock, tomato juice (I like salt-free V-8, which comes in several varieties of spiciness), or some combo thereof.
5. Season to taste. I suggest trying a few drops of tabasco (which is vinegar-based) or vinegar, which brightens the soup without making it taste like vinegar.
6. Optional: add solids such as leftover chopped chicken, lentils, rice, pasta bits.

I, for one, would find that extraordinarily useful.

Your question makes me think that an entirely separate post is in order on how to freeze vegetables and fruits to preserve them!

Dave–lettuce. Oy. What kind of lettuce? Romaine can be stir fried. Yes, you heard me right and it tastes fantastic. I know this because I had some cooked by Grace Young, author of The Breath of a Wok. Here is a link to the exact recipe she used for the dish that converted me to cooked lettuce: http://www.epicurious.com/recipes/food/views/233211

Lettuce soups are a classic of French cuisine–here is a link to a recipe for it–

http://www.epicurious.com/recipes/food/views/231995
While few Americans cook lettuce now, in the past, lettuce was more often cooked than eaten raw. Try looking up cooked lettuce on the internet and see if you can find some other great recipes.

Unfortunately, though, I don’t think you can freeze it without the quality suffering.

Good luck!