Preheat oven to 350°F. Grease a cookie sheet and set aside.

In a large bowl, cream together butter, brown sugar, and sugar on low speed until combined. Add egg and vanilla and beat on low until combined. Stir in peanut butter.

Add salt and baking soda to the bowl. Gradually stir in the flour. Stir until flour is fully incorporated in the mixture.

Roll dough into small balls and place on cookie sheet. Press the balls flat with a floured fork.

Bake for 10 to 12 minutes until golden. Let cool on a cooling rack.