1 pound crawfish tails
8 tablespoons salted butter
1 medium onion, chopped to equal 1 cup
3 tablespoons flour
1 tablespoon tomato paste
1/2 pint half and half to equal 1 cup
1/4 cup white wine (or more)
1 tablespoons chopped fresh parsley
1/2 teaspoon salt
1/2 teaspoon white pepper
1/4 teaspoon cayenne (or to taste)

Melt butter. Slowly add flour and whisk to make a paste. Add half and half, whisking all the while. When this is smooth, add the crawfish and spices. Heat thoroughly. This is better is made a day ahead and reheated.
I got this from my daughter a few years ago. If you like crawfish, you are sure to like this as well.