1. If eggs and milk are cold, before combining, submerge whole eggs in warm water 10 minutes and heat milk until just warm. Preheat oven to 450 degrees with a nonstick popover pan on rack in lowest position.

2. After you have combined eggs and milk in a large bowl, whisk together until very frothy. This should only take about 1 minute. Have the flour and salt measured out and ready to go.

3. Add flour and salt to egg mixture. We tested out a blender and an electric stand mixer when making the batter, but concluded that whisking by hand produces the most tender, airy popovers.

4. Whisk flour and salt into egg mixture just until batter is the consistency of heavy cream with some small lumps remaining. See those air bubbles? They are what will cause the popovers to rise.

5. Remove popover pan from oven and coat with cooking spray. If you prefer a standard muffin tin, only coat (and fill) the outer cups; they get better circulation in the oven. (Also, reduce baking time by 5 minutes.)

6. Fill popover cups about three-quarters full with batter. Combine thyme and Gruyere. Sprinkle over batter-filled popover cups. Bake 20 minutes, then reduce oven temperature to 350 degrees. Continue to bake until golden brown and dry to the touch, about 20 minutes more.

7. Popovers lose their crunch if they linger in the pan, so turn them out on a wire rack immediately and poke a small opening in the side of each with a paring knife to let the steam escape. Serve right away.