Cook your pasta per package instructions until it's al dente. Drain and set aside.
Place the shrimp in a plate or bowl—season with salt, pepper, and Creole seasoning. Toss to coat evenly, and set aside.
Add butter to a deep cast iron skillet. As soon as it melts and quits bubbling, add the shrimp. Cook until they start changing color, but don't go all the way because they'll finish cooking in the oven. Remove them from the pan and set aside.
Next, add the garlic and onions. Saute until the onion wilts, about 3 minutes.
Then whisk in the flour. Continue whisking until the butter and onion mixture completely absorbs the flour, then continue cooking for about a minute.
Gradually add the evaporated milk, followed by milk and broth; you don't want the roux to form any lumps. Simmer for 3-5 minutes or until the mixture thickens slightly.
Add more Creole seasoning and cayenne pepper if desired.
Finally, stir in the cheeses and continue stirring until they melt for an evenly combined and smooth sauce. Adjust seasonings to taste.
Add the macaroni to the cheese sauce, stirring until completely coated. Transfer your mac and cheese mixture into a lightly greased 2-quart baking dish and top with the remaining cheese. Arrange the shrimp on top.
Bake at 375℉ (190℃) for 10-15 minutes or until golden and bubbly.
Remove from the oven and top with chopped parsley, bacon, and bread crumbs if desired.