Make the Dough

1. Add the softened butter, light brown sugar, and peanut butter to a mixing bowl. Beat on medium speed until pale and fluffy, scraping down the sides and bottom of the bowl as needed.
2. Add the egg and vanilla extract. Continue mixing until well combined.
3. Place a sieve over the mixing bowl and sift in the flour, baking powder, and salt. Gently fold with a spatula until a dough forms and no dry ingredients remain.
4. Cover the bowl with cling film and refrigerate for at least 30 minutes, or until the dough is slightly firm to the touch.

Shape and Bake the Cookies

1. Towards the end of the chilling time, preheat the oven to 160°C fan and line a baking sheet with parchment paper.
2. Remove the dough from the refrigerator. Scoop about 1 tablespoon of dough and roll it into a ball. Place the dough balls on the prepared baking sheet, leaving about 5 cm (2 inches) between each one.
3. Gently flatten each dough ball with your hand to about 1 cm thick. Sprinkle the slightly crushed salted peanuts over the tops, gently pressing them into the dough so they stick.
4. Bake in the preheated oven for 15–16 minutes, or until the edges are lightly golden.
5. Remove the cookies from the oven and let them cool on the baking sheet for 10 minutes. They will be soft when they first come out of the oven but will firm up as they cool.
6. Carefully transfer the cookies to a wire rack and allow them to cool completely. Enjoy!