Popovers reheat well. You can make these early in the day and warm in a 350-degree oven.
Preheat oven to 425 degrees. Whisk together milk, flour, and 1 teaspoon salt. Whisk in eggs (mixture will be lumpy).
Heat two 6-cup popover pans in oven for 5 minutes. Generously brush cups with butter. Fill each cup a little more than halfway with batter. Sprinkle with cheese. Bake for 20 minutes.
Reduce oven temperature to 350 degrees. Bake until golden brown, about 25 minutes more. Let cool in pan for 5 minutes. Turn out popovers. Serve warm.