Preheat oven to 350 degrees F. Line a cookie sheet with parchment paper; set aside. In a small bowl stir together egg and peanut butter; stir in the 1/2 cup sugar, the baking powder, vanilla, and salt. If desired, stir in chocolate pieces. Roll dough by rounded teaspoonfuls into balls; roll in additional sugar and arrange on prepared cookie sheet. (Or drop by rounded teaspoonfuls onto prepared cookie sheet.) Flatten with a fork.
Bake for 10 to 13 minutes or just until set in center. Transfer to a wire rack; cool.