Cream the butter and peanut butter, then add in sugar and mix well.
Add in egg, then sift in flour, salt, baking powder and baking soda, mix until well combined. Chill the dough in fridge for an hour.
Take out about 2 tablespoons dough, roll into balls and coat with sugar. Place it on lined baking sheets, pop in preheated 180C oven, bake for 13-15 minutes. Enjoy!