Preparing the Lettuce

• Whether you purchased lettuce with the intention of using it in soup or are using up what you have before it turns bad, you don't want to just toss the entire head into the mix. Peel away and discard any leaves that look past their prime, and cut off the stalk at the bottom. Take a moment to rinse off the remaining leaves so that they are free of dirt and grit. Since they are going into soup, drying them with towels or a salad spinner shouldn't be necessary.

Complementary Flavors

• If you enjoy the taste of romaine lettuce on its own and don't want other flavors competing in the soup bowl, use then lettuce as the primary vegetable in the soup. However, if you like a more rounded taste with hints of other ingredients, try adding potato, onion, leeks, cauliflower or celery to the base. Add all of them, use some of them or try a different combination of vegetables to make the soup your own. Adding your favorite grated cheese at the end gives the soup a silky texture and flavor boost.

Basic Process

• The process of creating a romaine lettuce-based soup is relatively simple: All you have to do is gather and prepare your vegetable ingredients and cook them together until they have softened. Add stock to the pot and bring it to a boil to soften everything completely. Then you're ready to add cream and whatever herbs or spices you've decided on and puree it all together. An immersion blender is the most convenient way to blend the soup in the pot, but you can use a standard blender. If you puree hot soup in a regular blender, hold the lid on securely with a kitchen towel on top so that it stays on and you don't get burned.

Grilling the Lettuce

• One variation you may want to try - especially in the summer - grilling the romaine before you add it to the soup and puree it. Grilled romaine takes on the smoky, charred taste of the barbecue and adds a new dimension to your soup. Set your grill to medium-high heat, and then coat the lettuce leaves in olive oil before laying them on the rack. Turn the leaves on the grill continually for about 5 minutes or until they are brown and wilted, and then let them cool for a few minutes before you continue making the soup. You can also grill other vegetables that will go into the soup for an even smokier flavor.