Heat oven to 450°.
Spray popover pan with vegetable spray.
Add 1/2 tsp. of melted butter to each well in the popover pan.
Beat eggs until light and fluffy.
Add milk and beat well.
Gradually pour in the rest of the melted butter.
Add flour and salt and beat well. This is very important. In a stand mixer, you need to beat for 2-3 minutes. In a handheld mix, you need to beat for 4-5 minutes.
Pour a little more than 1/3 cup of batter into each part of the popover pan.
Bake for 20 minutes at 450° and then drop oven temperature to 325° for 15 minutes.
The popovers might look done on the outside, but they are not done in the inside. Let them cook for the full 15 minutes.
If your popovers did not rise far above the pan, it is because you did not beat them long enough.
Loosen from pan and serve warm with Jam Butter.
If using a muffin tin, bake for 15 minutes at 450° and 10 minutes at 325°.
If using mini muffin pans, bake for 10 minutes at 450° and 10 minutes at 325°.