Cook the macaroni according to package instructions until al dente. Drain and set aside.
Heat a large skillet over medium heat, add butter, and whisk in flour as soon as the butter melts, then continue whisking for about a minute until it's a light tan color.
Slowly add evaporated milk, a little at a time, followed by milk, constantly stirring because you don't want any lumps. Simmer for 3-5 minutes until the mixture slightly thickens. Turn off the heat.
Stir in the cheese (a little at a time), onion, garlic powder, salt, pepper, and Creole seasoning (if using any). Continue stirring until everything's melted, evenly combined, and smooth.
Add the pasta and stir until thoroughly combined, ensuring the sauce covers every macaroni for an even taste and texture. Adjust seasonings to taste.
Transfer the pasta mixture into a lightly greased 4-quart baking dish and top with the remaining cheese.
Bake at 375℉ (190℃) for about 12 minutes or until bubbly. Please don't overcook because it dries out the mac and cheese.
Optional: For an extra touch, lightly broil the top for 1-2 minutes for a slightly brown top.