How to Make It
In a medium saucepan, bring 3 1/2 cups of water to a boil with 1 tablespoon of the butter. Add a generous pinch of salt and gradually whisk in the grits. Cook over moderately low heat, whisking often, until the grits are thick and just tender, about 30 minutes.
Meanwhile, in another medium saucepan, melt the remaining 2 tablespoons of butter. Whisk in the flour, and when it is bubbling, gradually whisk in the milk. Cook over moderate heat, whisking frequently, until thickened and no floury taste remains, 8 to 10 minutes. Stir in the grated cheese and cook until just melted, about 2 minutes.
Using a rubber spatula, fold the Parmesan sauce into the grits and season with salt and pepper. Serve right away.