Preheat the oven to 350F. In a medium bowl, stir together the peanut butter, sugars and egg. If you like, add chocolate chips too - and stir until well blended and thick enough to roll into balls.
Roll the dough into 1-inch balls and place on a parchment-lined or ungreased baking sheet. Press down on each cookie with the tines of a fork. Bake for 12-14 minutes, until pale golden around the edges.