Preheat the oven to 350 degrees.
Place oven rack in the middle position.Using a hand mixer or a stand mixer, mix peanut butter and sugar till fluffy. Add the egg and mix till dough is smooth. Roll the dough into 2 - 2 1/2 inch balls. Roll in the extra granulated sugar and place on a non stick cookie sheet- about an inch to an inch and a half apart. Bake in the oven for 9 1/2 minutes.