Preheat the Oven: Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish.
Cook the Vegetables: Melt 2 tablespoons of butter in a large skillet over medium heat. Add the onion and bell pepper, cooking for about 5 minutes until softened. Stir in the garlic and cook for 30 seconds.
Prepare the Filling: Add the crawfish tails, Cajun seasoning, paprika, salt, and pepper. Cook for 2–3 minutes, stirring gently. Remove from the heat and mix in the Monterey Jack and cheddar cheese until well combined.
Make the Cream Sauce: In a saucepan, melt the remaining butter over medium heat. Whisk in the flour and cook for 1 minute. Gradually whisk in the milk until smooth. Simmer for 3–5 minutes until slightly thickened. Stir in the sour cream, Cajun seasoning, and Monterey Jack cheese until melted and creamy.
Fill the Tortillas: Spoon the crawfish filling evenly into each tortilla. Roll them tightly and place seam-side down in the prepared baking dish.
Add the Sauce: Pour the cream sauce evenly over the enchiladas. Sprinkle the remaining shredded cheese over the top.
Bake: Bake uncovered for 20–25 minutes, or until the cheese is melted, bubbly, and lightly golden.
Rest and Serve: Let the enchiladas rest for 5 minutes before serving. Garnish with chopped green onions and fresh parsley if desired.