2 1/2 cups whole milk
2 1/2 cups all-purpose flour
Coarse salt
6 large eggs
Unsalted butter, softened, for pans
1 cup coarsely grated Gruyere cheese (3 ounces)

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.