In food processor or by hand, combine sugar, peanut butter, egg and vanilla; stir in peanuts, if using.
Roll dough into small balls and place on greased baking sheet about 2 inches (5 cm) apart.
Flatten balls with tines of fork dipped in flour.
Sprinkle with chocolate chips, if using.
Bake in 325°F (160°C) oven for 12 to 13 minutes or until lightly browned.
Let cool on wire rack.