19x13 pan or smaller and spray with pam, To double recipe add 1 more chicken breast. In a bowl, add soup, sauce and mix well. Do not add water to soup! Add chicken, onion and 4 oz of chedder cheese, mix well. Crumble a half of the bag of doritos chips but not to much, Add to mixture. Pour in casserole dish and put in oven at 350 degrees for about 20-25 minutes. or until cheese begins to bubble. Take out of oven and crumble the rest of chips and sprinkle over top of dish and add rest of cheese. Then stick back in oven for an additional 3-5 minutes or just enough to melt the cheese. Take out of oven and enjoy!!