Preheat the oven to 400 degrees. Divide 1 tbsp of melted butter in each cup of a popover pan. Place the pan into the oven and allow it to heat through.
Add the eggs to a bowl. Whisk until frothy.
Slowly add your flour while continually whisking. The goal is to have a smooth batter before adding the milk.
Continue to whisk while drizzling in the milk. The batter will be thin like a pancake batter.
Mix in the salt and melted butter.
Carefully remove the hot pan from the oven.
Divide the batter between the 6 cups.
Sprinkle blueberries over the top if adding.
Let the popovers bake for 30-35 minutes or until puffed and golden brown.
Dust powdered sugar over the top of the blueberry popovers if desired.