Preheat oven to 400˚F. Place a baking sheet on a rack in the lower third of the preheating oven (Remove other racks or move them so there is a clearance of 5 or 6 inches between racks.)
Melt butter. Place ½ teaspoon butter into bottom of each cup of a 12-cup standard muffin pan or 2 6-cup muffin pans; set aside.
Combine remaining melted butter, milk, eggs, sugar and blend until smooth. (Use a blender or whisk by hand), Add flour and blend until smooth.
Place prepared muffin pan in oven on preheated baking sheet. Heat until butter is fully melted.
Remove muffin pan on pan sheet from the oven. Evenly distribute batter between 12 muffin cups.
Return filled muffin pan on baking sheet to oven. Bake 30 to 35 minutes or until popovers are well browned and crusty. Do not open oven until last 5 minutes to avoid deflating the popovers.
Remove popovers from oven and remove from pan on to a wire rack. Serve immediately.