Combine first 3 ingredients in a medium bowl. Whisk together milk and next 3 ingredients. Whisk milk mixture into flour mixture, whisking until smooth.
Place popover pans or 6 (8-ounce) custard cups heavily coated with cooking spray in a 450° oven 3 minutes or until a drop of water sizzles when dropped in them. Remove pans from oven, and place on a baking sheet, filling cups half full with batter.
Bake at 425° for 30 minutes. Turn oven off; remove pans from oven. Cut a small slit in popover tops; return to oven. Let popovers stand in closed oven 3 minutes. Serve immediately.