Preheat oven to 350 degrees and line a cookie sheet with parchment paper
In a small bowl, mix together flour, baking soda, and salt; set aside.
Using a standing mixer, cream together butter, brown sugar and peanut butter.
Mix in the egg and vanilla until combined.
Gradually mix in the dry ingredients until just blended.
Form dough into 1 inch balls.
Shape into a log and roll log in sugar.
Place logs on cookie sheet about 2 inches apart.
Using the tines of a fork, make a criss-cross pattern in the dough.
Pinch the middle of the cookie to make a peanut shape.
Bake 10-12 minutes, until lightly browned on the edges and still soft in center.
Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.