In a bowl, mix together the flour, baking powder and baking soda listed under dry ingredients.
In a separate bowl, cream the peanut butter, butter, caster sugar, and brown sugar till pale and fluffy. Use an electric mixer on medium speed.
Add the egg and beat for 3-5 minutes on medium speed, till light and thoroughly mixed in. Add the vanilla extract and give it a quick mix.
Spoon the dry ingredients into the wet ingredient. Gently fold in until completely incorporated.
Cover the bowl with a cling film and chill in the refrigerator for 30 minutes.
Preheat the oven at 180 degrees Celcius for 10 minutes.
Roll out even sized balls from the Peanut Butter cookie dough. Roughly around 30 g each.
Line a cookie sheet with parchment paper or Silpat. Place the cookie dough balls on the sheet. Flatten and mark it with the back of a fork, to a thickness of ½ inch.
Bake for 10 minutes; rotating the sheet halfway at 5 minutes to avoid burning. Cookies are done when the bottom is golden brown and it begins to brown at the sides.
Remove from the oven and let it cool down in the pan for 15 minutes. Enjoy!