To make a chile relleno casserole, place 7 ounces of green chile peppers in a baking dish, and cover them with 4 ounces of Monterrey Jack cheese, 4 ounces of Cheddar cheese and 7 ounces of peppers. Beat together 2 eggs, 5 ounces of evaporated milk, 2 tablespoons of flour and 1/2 cup of milk; transfer the mixture to the dish; and bake for 25 minutes. Add 8 ounces of tomato sauce, bake for 15 minutes, and top with cheese.
Alternatively, cook 1 pound of lean ground beef and 1 chopped onion in a skillet for 5 to 10 minutes, and drain excess liquid. Place 4 ounces of whole green chile peppers on the bottom of a baking dish, add 3/4 cups of shredded Cheddar cheese on top, and cover everything with beef. Sprinkle the beef with another 3/4 cups of shredded cheese, and top with 4 ounces of chile peppers. Beat 4 eggs, 1/4 cup of all-purpose flour and 1 1/2 cups of milk until the mixture is well combined; transfer the mixture to the baking dish; and add salt and pepper to taste.
Bake the casserole for about 45 to 50 minutes at 350 degrees Fahrenheit, remove the dish from the oven, allow it to cool for several minutes, and serve the casserole.