Preheat the oven to 180C / 350F and line a baking tray with baking paper.
In a mixing bowl, beat together the butter and sugar until light and fluffy. Beat in the egg and milk and blend well. Sift in the flour and cocoa powder and mix to form a dough. You may need to use your hands to incorporate the last of the flour and bring the dough together into a ball.
Roll out the dough on a lightly floured surface to around ¼ inch thick.
Use a cookie cutter to cut out as many cookies as you can, re-rolling the dough with any offcuts to make more cookies.
Place the cookies on the baking tray and cook for 10-12 minutes, or until golden brown.
Leave cookies to cool for a few minutes on the tray and then transfer to a wire rack to cool completely.
Place the icing sugar and orange juice in a bowl and combine with a wooden spoon until an icing has formed. Spread the icing over the cookies and then leave to set.
Drizzle the melted chocolate over the cookies and leave to set once again before serving.
