Prepare the dough: put the sifted flour, cocoa and baking powder in a large bowl and make a well in the centre. Add the lightly beaten egg, butter and icing sugar.
Knead quickly with your hands, mixing all the ingredients together. Shape the dough into a ball, flatten it and cover with cling film. Place in the fridge to rest for an hour.
Take the cocoa dough and, with the rolling pin, roll it out to a thickness of about 1/2 centimetre. With a small round cutter, cut out the biscuits. Roll the biscuits in the palm of your hands to form balls and place them on a baking tray lined with baking paper.
Bake in a preheated oven at 180° for 10 minutes. Leave to cool completely, preferably overnight. With a sharp knife, cut a small hole in the centre of each biscuit, on the flat side. Using a teaspoon, pour a little coffee into each hole. Join the biscuits two by two with Cremadelizia Pistacchio Babbi.