Set your oven to 350°F to preheat.
Bring the crawfish or seafood stock up to a boil in a large pot.
Add the elbow macaroni to the boiling stock and cook until just tender, about 6 minutes. Drain the pasta, reserving a cup of the cooking liquid.
While the pasta cooks, melt the butter in a 10-inch cast iron skillet over medium heat.
Whisk in the flour, cooking it for a couple of minutes until it forms a smooth paste.
Warm the milk separately, then gradually add it to the roux while stirring constantly to prevent lumps.
Stir in 2 cups of the grated Colby cheese until fully melted.
Mix in the Creole seasoning.
Combine the cooked noodles and crawfish tails into the cheese sauce and stir everything together.
Sprinkle the remaining cheese evenly on top, and bake in the oven uncovered for 15 minutes.
Switch the oven to broil and cook the top for an additional 3 minutes until golden and bubbly.
Remove the skillet carefully and garnish with a pinch of fresh parsley.
Serve hot and enjoy your hearty crawfish mac and cheese.