Cover the bottom of your casserole dish with tator tots and place in the oven (while it's still cold and warming up). Leave them there until you are ready to assemble the casserole. Mine were cooked about ½ way when I pulled them out to put my casserole together. I put them on a plate while I put all of my other ingredients in the casserole dish and then added them back to the top before putting everything in the oven to finish cooking.
In a medium skillet cook your sausage over medium heat until browned. Remove from skillet and set aside on a plate. Drain the grease and lightly wipe most of the remaining grease out (you want to leave a little bit to cook your onions).
Add your onions and garlic and cook until soft, about 4 minutes.
Add your hamburger back to your skillet with the onions and garlic. Add Rotel tomatoes, garlic powder, onion powder, black pepper,crushed red pepper and stir well. Let cook over medium heat until most of the liquid from the Rotel tomatoes has cooked off.
Add your sour cream, cream of mushroom soup, drained corn, ½ of your cheese and milk. Stir well. Let cook until cheese is melted.
Put your cheesy meaty mixture in the bottom of the casserole dish. Add your olives if using, and ½ of the remaining cheese.
Add your layer of tator tots and press down a little bit to make sure they are stuck in the mixture just a little bit. Cover the top of the tator tots with your remaining cheese and chives.
Cook in the oven for 20-25 minutes or until the cheese is all the way melted and you can see the casserole bubbling up on the sides and the middle just a bit.