Preheat oven to 450 (230 C) degrees for at least 25 minutes. Lightly coat a 6-cup popover pan with oil or cooking spray.
Whisk together the milk, eggs and butter in a large bowl until blended. Add the remaining ingredients and mix well.
Place the empty pan in the oven to heat for 7 minutes. Carefully remove from the oven and fill the cups evenly with the batter (this is less messy if you transfer batter to a 4-cup liquid measuring cup).
Bake for 18-20 minutes, then lower the oven temperature to 350 (175C) degrees. Continue baking until the popovers are deep golden brown, 15-18 more minutes.
Cool for 3 minutes in the pan before removing to a rack. Serve warm.
This recipe makes 6 popovers as prepared in a 6-cup popover pan. If you don't have one, use a standard muffin tin to make 10 small popovers.
Make ahead: The batter may be prepared and kept refrigerated up to 1 day in advance. About an hour before baking, take the batter out of the fridge to bring to room temperature. Stir it well in case it has separated.
.Reheat cooled popovers in a 350 degree oven for about 10 minutes. They won't be as puffy, but still taste great!