My Cajun mother makes a wonderful mirliton casserole for the holidays that's always a hit. I had a craving for mirliton and crawfish one day, and pieced together this soup from several recipes and a few traditional Cajun cooking methods. Some people prefer to peel and pit mirliton before using them, but the whole fruit is edible. Crawfish tails are usually mostly cooked before being peeled and bagged, but it's best to be on the safe side. Sauteing them first makes sure that they are fully cooked and flavors the butter for the rest of the soup.