Add the ground beef and diced onion to a large skillet and cook over medium-high heat until no pink remains.
Add to a large mixing bowl, along with the shredded hashbrowns, pepper jack cheese, cream of mushroom soup, sour cream, milk, salt and creole seasoning. Stir to combine.
Empty into a 11x7" Casserole Dish, evenly, and bake in the oven for 30-35 minutes until bubbling around all edges.
Top with the remaining colby jack cheese and bake again another 5 minutes.