Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
- Cream the butter and sugars: In a large mixing bowl, beat together the softened butter, peanut butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
- Add Wet Ingredients: Beat in the egg and vanilla extract until well combined.
- Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
- Mix Dry Ingredients into Wet: Gradually add the dry ingredients to the wet mixture, mixing until just combined.
- Shape the Cookies: Scoop out approximately ¼ cup of dough for each cookie and roll into a ball. Roll in additional granulated sugar to coat. Flatten each dough ball slightly with your hand or spoon.
- Bake: Bake for 8–10 minutes, or until the edges are lightly golden. Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.