Brown ground beef in a large stock pot, add onions, tomatoes, chili mix, chili beans, mushrooms and the can of spaghetti. Bring to a boil on top of stove, then simmer for 15 minutes. In large casserole dish crumble the chips in the bottom, (leave a few to go on top). Add chili mixture then cheese (again leaving some for the top). Place the left over chips on top and cheese. Bake at 350* until bubbly hot.