Mix butter and peanut butter until smooth and creamy. Leave at room temperature for 1 hour beforehand for easier mixing.

Add sugar and salt to the butter mixture and mix well.

Whip the mixture slowly until sugar is incorporated, then mix at high speed for 2 minutes until light ivory color.

Add 1/2 beaten egg to the mixture and mix for another 2 minutes.

Sift flour and baking powder together, then add to the butter mixture.

Use a spatula to mix the dry ingredients into the wet mixture until a cohesive dough forms.

Spoon dough onto a baking tray, leaving space between each cookie.

Preheat oven to 180°C and bake cookies for 10 minutes. After 3 minutes, press cookies with a mug to create cracks.

Return cookies to the oven and bake for another 7 minutes.