Preheat your oven to 375°F (190°C).
Place the halved French bread on a baking sheet, cut side up. Spread the compound garlic butter generously over each piece. (Make sure to reserve 2 tbs of compound butter)
Place the bread in the preheated oven and bake for 10 minutes, or until the slightly golden brown and butter has melted into the bread. Remove from oven and set aside.
In a skillet over medium heat, melt 2 tablespoons of the reserved compound garlic butter.
Sauté the red bell pepper, onion, celery, and garlic until softened, about 5 minutes.
Add the crawfish tails and sprinkle in the Bayou city seasonings (or creole seasoning of your choice). Stir to combine and cook for an additional 2-3 minutes. Remove from heat and let cool slightly.
In a large bowl, mix the sautéed crawfish mixture with mayonnaise, mozzarella, mild cheddar, roasted garlic (optional), and green onion until well combined. season with salt and pepper to taste.
Spoon the crawfish mixture evenly onto the buttered bread halves, spreading it to cover the surface.Top with more cheese if you would like.
Place the bread in the preheated oven and bake for 12-15 minutes, or until the cheese is melted and bubbling. For a golden finish, broil for an additional 1-2 minutes.
Remove the crawfish bread from the oven, sprinkle with parsley, and let cool slightly before slicing into portions.