Mix butter, sugar and, egg in a mixer until well-blended.
In a separate bowl, mix together flour, baking powder, and salt.
Add flour mixture and milk alternately to the creamed mixture.
Fill muffin cups ⅔ full.
Bake 20-25 minutes or until golden brown.
Immediately roll each puff in the ½ cup melted butter, then into the sugar.
Using the back of a rounded spoon, depress the center. Then fill with about 1 teaspoon of jam, to your liking.
Serve warm.
Notes
You can add 1/2 teaspoon cinnamon to the sugar before rolling the puffs to create a really good cinnamon sugar puff. I have had this recipe for many years.