Preheat oven to 450 degrees. Coat the cups with room-temperature butter and then pour ½ teaspoon melted butter into each cup, reserving remaining butter. This helps release popovers from the cups after baking.
Whisk together flour and salt. In a separate bowl, whisk together milk and eggs.
Pour wet ingredients into the dry mixture and whisk until combined. Finish the batter by whisking in remaining melted butter. For a savory variation, try adding ¼ cup shredded Gruyère to the batter or add 1 tablespoon chopped thyme or basil.
Divide the batter between 6 cups. Bake for 20 minutes on the bottom rack of oven. No peeking! Popovers will deflate if you open the oven door.
Reduce the heat to 350 degrees and bake for 10−15 minutes more, until a deep golden brown. The longer you bake them, the sturdier they will become, but be careful not to overbake. Continue to keep the oven door closed!
Spread, Fill, or Eat As Is / Enjoy popovers with butter and honey or jam. Because the middle of the popover is hollow, popovers also make great edible bowls. Try filling them with tuna salad for lunch or ice cream topped with fudge sauce for dessert.