Preheat the oven to 350 degrees. Then line two baking sheets with parchment paper or silicone baking mats.
Cream butter, peanut butter, brown sugar, and granulated sugar together until light and fluffy. Add in egg and vanilla. Mix until combined. Stir in baking soda and flour until just combined.
Scoop into evenly portioned balls onto the baking sheets. Then with the back of a fork squish each cookie dough ball down, creating that classic criss-cross look.
Bake for 7-8 minutes. Cool on the baking sheet for 3 minutes then transfer to a cooling wrack.