Preheat the oven to 180° C and line a tray with parchment paper.
Place cocoa powder, sugar and flour in a medium mixing bowl, and add the chilled butter.
225 g all-purpose flour, 25 g cocoa, 125 g sugar, 125 g butter
With your palms facing upwards, use your fingertips to rub in the butter until the mixture resembles sand. Add the egg, mix and knead well on a lightly floured, cool benchtop.
1 egg
Shape the pastry into a disc, wrap well in cling film and place in the fridge for 1 hour to rest.
On a piece of parchment paper, roll the dough to a thickness of 3 mm, then cut out the cookies. If you don't mind the extra sugar, sprinkle the cookies with extra sugar - it makes them prettier!
sugar for decorating
Place the cookies in the prepared tray and cook for 10-15 minutes.
Store in a tin box or an airtight container.