Preheat the oven to 350ºF.

Melt the butter in a large heavy Dutch oven over medium heat. Add the onions, bell peppers, and celery and cook, stirring often, for 10 minutes, or until they are wilted and pale gold. Add the flour and cook, stirring· often, for 2 minutes. Add the parsley, shrimp, and crawfish. Cook, stirring often, for about 5 minutes, or until the shrimp turn pink. Add the half-and-half, cheese, jalapeños, and garlic. Stir until the cheese is completely melted and the mixture thickens, about 5 minutes. Season to taste with the salt and cayenne.

Arrange the fettuccine in a 3-quart casserole and pour the seafood mixture over it evenly. Sprinkle the top of the casserole with the Parmesan cheese. Bake for about 10 minutes, or until the mixture bubbles.

Excerpted from Cooking Up a Storm