Blend peanuts into fine crumbs, set aside.

Sift all purpose flour, icing sugar, cocoa powder, salt and baking powder into a bowl. Add in previously ground peanuts and mix well to combine.

Add in egg yolk and vanilla extract. Mix well. Then slowly pour in sunflower oil while mixing. Bring the dough together into a ball, using your hand.

Take around 1 teaspoon of dough and form it into a ball. Place it on a baking tray with a baking sheet. Lightly press peanut halves on top.

Bake in a preheated oven at 300ºF (150ºC) for 10 minutes or until the cookies are fully cooked. Leave them on the tray for 5 minutes or until almost cooled. Only then transfer to a rack and leave them to cool completely. They will break apart if you touch them while they're still hot.