Mix Bisquick, refried beans and water. Pat into bottom of large baking dish. Brown ground beef and add chopped onion. Drain. Spread on top of crust tin baking dish. Then layer taco sauce and 1 cup cheese. Bake at 350 degrees until done (when you can lift the side up and it doesn't not stick or fall apart.) Let cool a little and then top with shredded lettuce, diced tomatoes, grated cheese and sour cream.