In a large bowl combine meat, Shake and Bake, dry, soup mix, mushrooms and egg; set aside.
In a small bowl combine 1/2 cup cheese soup and evaporated milk. Add to meat mixture. Mix well and form a loaf. Place on top of potatoes, keeping it from touching the sides of crock pot.
Mix remaining cheese soup and mushroom soup together. Pour over top. Slice onion and place over all. Cook on high for one hour, then on low for 5-6 hours.