A friend gave me a "King Arthur Flour Baker's Companion" cookbook for my birthday one year and my son found this recipe. I made them for the in my muffin tins at first, then I bought a Popover pan. They are great just as the recipe or you can add fresh shredded parmesan and dried herbs for a more savory popover. We also stuff the leftovers with ham and cheese, then heat until the cheese is melting.
Place all of the ingredients in a blender in the order indicated above. Blend for 30 seconds, stopping midway through to scrape down the sides of the blender. Allow the batter to rest for 15 minutes.
Using cooking spray, thoroughly grease 12 muffin cups or 6 popover cups. Be sure to grease the area around the cups as well as the cups themselves. Fill the cups about two-thirds full with the batter. Bake for 20 minutes, then reduce the oven to 350 degrees and bake for an additional 10 minutes.
Resist the urge to open the oven door any time during this process.
Remove the baked popovers from the oven, pierce the tops with a knife, and allow them to cool in the pan for 5 minutes. Then gently turn them out of the pan onto a wire rack. Serve warm.