Preheat the oven to 350 degrees F (180 degrees C). Heat Unsalted Butter (2 tablespoon) in a pan.
Into the butter, add your Onion (1/2 cup), Celery (1/2 cup), and Red Bell Pepper (1/2 cup). Add some Salt and Pepper (to taste). Saute for 5 minutes.
Add Garlic (1 clove) and Fresh Thyme (1 1/2 teaspoon) into the pan.
Add your Frozen Crawfish Tails (1 pound). Cook up, add Salt (1 teaspoon) and Cajun Seasoning (1 tablespoon). Cook for about 3 minutes.
Add some Scallion (1 handful). Turn off fire, stir them in, and let it cool down for a few minutes.
Add Mayonnaise (1/2 cup) and Creole Mustard (2 1/2 teaspoon) and mix.
Add Provolone Cheese (4 ounce) and Extra Sharp White Cheddar Cheese (4 ounce) and mix together.
Slice the French Roll (3) in half, and put some crawfish on the bottom of the french bread and close it up.
Prepare a sheet of tin foil. Rub the tops of the French rolls with Butter (1/2 tablespoon).
Wrap the French rolls and bake in the preheated oven for 20 to 25 minutes.
Slice it diagonally and serve immediately. Enjoy!