Melt butter, on medium heat, in a skillet. Once melted add in 1 cup trinity (onion, bell pepper, celery) and cook for 5 minutes. Add in crawfish, old bay, 1 teaspoon creole seasoning, 1 teaspoon onion powder, 1 teaspoon garlic powder, and cook for another 5 minutes. Set aside and let cool.
In a bowl, combine mayonnaise, mozzarella, parmesan, cheddar, creole mustard, and the remaining seasonings (dry mustard, creole seasoning, onion powder, garlic powder. Fold in you crawfish mixture as well as your roasted garlic.
half your French bread length wise and spread your crawfish mixture evenly on each. (you can top with any leftover mozzarella to make it extra CHEESY)
Place bread in the oven with topping facing up and bake for 15 minutes.
Remove from oven and top with parsley. Serve warm.