Instructions

• Preheat the oven to 375°F (190°C). Position a rack in the lower-middle area of the oven so there is at least 5 inches (13 cm) of space above it for the popovers to rise. Place a 12-cup muffin pan in the oven to heat while you make the batter.
• In a large mixing bowl, whisk together the 3 tablespoons melted, slightly cooled unsalted butter, the 5 large eggs, and 1½ teaspoons salt until combined.
• Whisk in half of the 1½ cups milk. Add the 1½ cups all-purpose flour (spooned into the measuring cup and leveled off) and whisk until the batter is completely smooth. Whisk in the remaining milk until combined and smooth.
• Carefully remove the hot muffin pan from the oven. Generously spray the entire pan, including the areas between the cups, with non-stick cooking spray.
• Pour or ladle the batter into the prepared muffin cups, filling each cup to just below the rim.
• Evenly sprinkle the 3 oz finely shredded Gruyère (optional) over the batter in the cups, if using.
• Return the pan to the oven and bake until the popovers are well risen and deep golden brown, 40 to 50 minutes. Do not open the oven door before 35 minutes, or the popovers may collapse.
• Remove the pan from the oven. Using oven mitts, lift the popovers out of the pan and place them on a serving platter. Serve immediately; they will deflate slightly as they cool.