Using large saucepan saute the onions in margarine until soft Blend in flour, chicken cube, salt, mustard and pepper. Slowly stir in evaporated milk, then add broth and soups. Stir constantly until sauce thickens. Add chicken to sauce, then noodles.
Spray large baking dish with Pam. Bake at 350 for 30 minutes. Sprinkle cheese on top and bake until golden bubbly.