In a mixing bowl, combine the flour, baking powder, and salt and set aside.

In a stand mixer with paddle attachment, on medium-high speed, beat the butter until smooth. Add the peanut butter and beat until combined.

Add the brown sugar and granulated sugar, continuing to beat until evenly mixed. Incorporate the eggs one at a time, allowing a minute between additions. Add the vanilla.

Reduce the speed to low and gradually add the flour mixture, mixing until just combined. Transfer the dough to a mixing bowl, cover, and refrigerate for 30 minutes.

Preheat the oven to 350°F (gas mark 4).

Using a cookie scoop, roll out 2 tablespoons of dough and roll into a ball. If desired, roll in sugar before placing on a lined baking sheet. Flatten the dough with a fork or bottom of a glass, dipping in sugar after each impression.

Bake for 12-15 minutes or until the edges start to turn golden. Allow to cool for 2 minutes before transferring to a cooling rack.