2
Stir the onion, flour, salt, and pepper into the butter remaining in the saucepan. Cook for about 1 minute, stirring constantly. Gradually add milk, stirring constantly, until mixture is smooth.
Increase heat and bring to a boil, still stirring. Remove from heat. Add cheese and stir until melted. Next add spinach and mix well. Add eggs and remaining cereal. Mix.
Pour into a 1 quart casserole dish. Sprinkle reserved topping (crushed corn flakes and butter) over all and bake for 25 minutes or until heated through.