Bring all cold ingredients to room temperature.

Heat the oven to 400°F.

Grease a 6-cup popover pan with the 1 teaspoon of butter.

Combine the 1 tablespoon of butter, the flour, salt, eggs and milk in a food processor or blender and process for 30 seconds.

Divide the batter evenly among the cups of the popover pan, filling each one-third to one-half full. Bake on the middle rack of the oven for 40 minutes, taking care not to open the oven door. Remove the popovers to a cooling rack and pierce each one in the top with a knife to allow steam to escape. Serve warm.