Heat oven to 350°F.

In large bowl, beat butter and sugars until light and fluffy (~2-3 minutes). Beat in peanut butter. Add egg and vanilla and beat to combine. Combine flour, baking soda and salt. Add to peanut butter mixture and beat until mixed. Fold in chopped peanuts, if using.

Roll dough into 1"balls. Place cookies on lined baking sheets ~2" apart. Use fork dipped in granulated sugar to make crisscross pattern on cookies.

Bake ~10-12 minutes, or until lightly browned around edges. Cool on wire rack.