Core the jalapeno peppers as shown in the above pictures.
Saute the butter, onion and garlic until the onion is tender, about 5 minutes. Add the crawfish and cajun seasoning. Cook for a few more minutes, stirring so all the crawfish are cooked. Cool completely. Remove 20 crawfish and set aside. If desired, you can chop/mince the crawfish mixture that is to be mixed with the cheese. This healps spread the crawfish throughout the cheese mixture and makes it easier to stuff the peppers.
Make the filling by mixing the cream cheese, cheddar cheese, and crawfish mixture.
Fill the peppers with the filling and top with a crawfish.