Coat a 9x13-inch baking pan with cooking spray. Bring milk and 1 stick of butter to a slow boil in a saucepan over medium-high heat. Stir in grits, salt, and pepper. Cover, reduce heat to medium-low, and cook, stirring occasionally, until thickened, about 5 minutes. Pour into the prepared baking pan. Place in the refrigerator until firm, at least 1 hour. Preheat the oven to 400 degrees F (200 degrees C). Remove chilled grits from the refrigerator and cut into rectangular pieces. Remove pieces from the baking pan and then drop them back into the pan randomly, as if they were falling domino tiles. Pour melted 1/2 stick butter over grits and sprinkle with Swiss and Parmesan cheeses. Bake in the preheated oven until grits are cooked through and cheese is melted, 25 to 30 minutes.