Soften the butter. Mix this with both sugars, the orange zest and juice.
Add in the eggs and mix again.
Add in the flour, cocoa, bicarb and salt. This will form your thick cookie dough.
Add the chopped chocolate and mix through the cookie dough until evenly distributed.
Separate your cookie dough into 10 balls. Pop onto a lined baking tray and freeze for 20 minutes.
Preheat your oven to 160 fan. Separate the cookies onto two baking trays and bake for 12 minutes. The cookies will be soft when you take them out of the oven but leave them on the tray for 20-30 minutes. While they are cooling, melt the white chocolate. Divide this into two and colour one half orange. You’ll need two piping bags, to put the melted chocolate into. Snip a little off and decorate one half of each cookie. Finish with some festive sprinkles.