Preheat over to 450° F.
Grease popover tin with butter.
Beat together flour, salt, eggs, and milk until mixed, approx. 15 seconds.
Let batter rest for ½ hour.
Ten minutes before the ½ hour is over, place greased popover tin in the oven to get hot.
After the resting period is over, stir 1 tablespoon melted butter to the batter.
Remove popover tin from oven and quickly fill the cups with batter, so that each cup is ½ to ⅔ full.
Bake for 15 minutes at 450°.
Reduce the temperature to 400° and bake until popovers are puffed and brown, approx. 15 minutes more. Do not check the popovers until they have baked a total of 30 minutes.
Remove from pan immediately and serve hot.
