Heat oven to 400ºF.
Grease a 6-cup popover pan with 1 tablespoon of butter.
Place all of the ingredients into a food processor or blender and process for 30 seconds. Divide the batter evenly between the cups of the popover pan, each should be about 1/3 to 1/2 full. Bake on the middle rack of the oven for 40 minutes.
Remove the popovers to a cooling rack and pierce each in the top with a knife to allow steam to escape. Serve warm.