Cook the Pasta: Boil a large pot of salted water and cook the pasta according to package directions until al dente. Drain and set aside.
Make the Roux: In a large saucepan, melt butter over medium heat. Whisk in flour and cook for 1-2 minutes until bubbly and golden.
Add Dairy: Slowly add evaporated milk and heavy cream, whisking constantly to avoid lumps. Stir in Dijon mustard and season with salt, pepper, garlic powder, and smoked paprika. Allow the sauce to simmer for a few minutes until thickened.
Melt the Cheese: Gradually add the shredded mozzarella, colby jack, and sharp cheddar to the sauce, stirring constantly until the cheese is fully melted and the sauce is smooth and creamy.
Combine Pasta and Sauce: Add the cooked pasta to the cheese sauce and toss gently to combine. If the sauce is too thick, add a splash of reserved pasta water to reach your desired consistency.
Bake: Preheat the oven to 350°F (175°C). Transfer the pasta mixture into a greased casserole dish. Top with additional shredded cheese, if desired. Bake for 25-30 minutes or until bubbly and golden brown on top.
Optional Broil: For an extra crispy top, turn on the broiler for the last 2 minutes of baking, watching carefully to avoid burning.
Serve: Garnish with freshly chopped parsley or chives and serve hot.