First crunch the bags of chips up to little pieces. Then dump it into a large bowl. Add the cream of mushroom soup one can at a time. You don't want it too runny, just a little sticky to the touch. Then add the tuna fish, mushroom, mixed vegetables and stir it all together.
Place it into a casserole dish.
Cook it for about 45 minutes. Take it out about 10 minutes before and add the cheese to the top. Cook until the edges are golden brown or the cheese is melted.