Brown the sausage in a skillet, then cook the onion alongside the meat. Remove the sausage and onion from the skillet, then add in the hash browns (you want them to crisp up a bit). Place the hash browns in the bottom of a greased 8×8-inch baking dish. Top with the sausage mixture and half of the shredded cheese.
https://ohsweetbasil.com/cheesy-sausage-hash-brown-breakfast-casserole-recipe/