
Bring a large pot of water to a boil, add a spoonful of salt, and cook the macaroni to al dente according to package instructions. Drain it in a colander and set aside.
Melt butter in a large skillet over medium heat. Whisk in the flour as soon as it melts and continue whisking for about a minute until it's a light tan color.
Slowly add milk, whisking as you go so no lumps form. Simmer for 3-5 minutes until mixture slightly thickens. Then turn off the heat.
Spread the Velveeta and ¾ of the cheddar cheese over the gravy in the skillet. Stir until thoroughly mixed.
Stir in the onion, garlic powder, pepper, and Creole seasoning (if using). Continue stirring until everything's melted, evenly combined, and smooth.
Add the pasta and mix until thoroughly combined, ensuring the sauce coats every macaroni. Adjust seasonings to taste.
Transfer the pasta mixture into a lightly greased 4-quart casserole dish. Top with the remaining cheese.
Bake at 375℉ (190℃) for about 12 minutes or until bubbly. Avoid overcooking so your mac and cheese doesn't dry out.
Optional: Add some breadcrumbs and lightly broil the casserole for 1-2 minutes for an extra golden top.
Sprinkle with chopped parsley and more cheese if desired. Let it rest for 5-10 minutes and serve hot.