Preheat the oven to 350 degrees F. Grease a 9-by-12-by-2-inch casserole dish.
Cook the grits in the boiling water with the salt until thickened, about 5 minutes. Add the cheese and butter to the hot grits and stir until melted and incorporated. Beat the eggs and add the milk to the beaten eggs. Slowly stir the egg mixture into the grits. Pour the mixture into the prepared dish. Pour the melted butter over the cornflakes and stir to distribute the butter. Sprinkle the crumb mixture on top of the grits. Bake for 45 minutes.
Adapted from "Georgia Cooking in an Oklahoma Kitchen" by Trisha Yearwood (c) Clarkson Potter 2008. Provided courtesy of Trisha Yearwood. All rights reserved.