Preheat the oven to 450°F (232°C). Lightly coat a 12-cup popover pan or muffin tin with melted butter, oil, or baking spray.
Whisk together the milk, eggs, and butter in a large bowl until blended. Add the all-purpose flour, salt, black pepper, and Parmesan cheese, and mix well.
Place the empty pan in the oven and heat for 7 minutes. Carefully remove it from the oven and fill the cups evenly with the batter. (Transfer the batter to a liquid measuring cup for easy pouring into the pan.)
Bake for 18-20 minutes, then lower the oven temperature to 350°F (180°C). Continue baking until the popovers are deep golden brown, about 15-18 more minutes. Cool briefly in the pan. Serve warm.