Butter the popover pan and place it in the oven. You'll want the pan to be hot before you put the batter in it. (You should hear a sizzle in the pan when you add the batter.)
In a large mixing bowl, stir together the flour and salt.
Mix in the milk and blend with an electric mixer until totally smooth.
Beat in the eggs and butter.
Pull the hot pan from the oven (please use a pot holder!), and pour the batter in. Fill them about 3/4 of the way.
Bake for 35 minutes.
Remove from oven and let sit for about 5-10 minutes. Then turn the popovers upside down onto a clean surface. Cool on a plate or cooling rack, but don't let them cool completely before cutting one open and putting butter on it!
Eat one right there at the counter, because... warm bread with butter. YUM!
Please note that the nutrition data given here is a ballpark figure. Exact data is not possible.