In a large skillet, cook beef and onion till brown. Drain. Stir in tomato sauce, water and taco seasoning mix. Heat through. Remove from heat.
Beat eggs then stir in the milk. Add a small amount of the tomato sauce mixture to the eggs mixture, stirring constantly. Return all to skillet. Stir in kidney beans, 1 cup
Monterrey jack cheese and the crushed taco or tostada shells.