Slice onions thin, then pile in crockpot. You can use as many onions as you want. Top with up to a 1/2 cup of butter, put on low and cook overnight (about 10 hours). Wake up to the smell of onions cooking. If they are not browned to your liking, turn up to high for about 1-2 hours. You can also dump in the rest of the ingredients for french or regular onion soup.