Chocolate Orange Cheesecake

Smash the digestive biscuits into a fine crumble with a mortar and pestle.
Grate in the zest from one of the oranges an then squeeze in the juice.
Melt down the butter in a sauce pan.
Pour the melted butter into the biscuit crumbs.
Mix until well combined. The chocolate will melt into the butter.
Tightly pack the crumbs into the bottom of a cake tin and chill for an hour.
Put the icing sugar and cream cheese in a bowl.
Whisk together until smooth.
Break a third of the chocolate orange into a bowl and melt in the microwave.
Mix the melted chocolate into the cream cheese.
Add the Chocolate Orange liqueur.
Whisk in the cocoa and then beat in the eggs, one at a time.
Pour the cream cheese over the biscuit base.
Bake in an oven at 180'C for 50 minutes until firm.
Grate the second orange into a bowl and put to one side. Squeeze the juice from the orange into a pan and stir in the sugar, heating gently until dissolved.
Simmer the syrup until it begins to thicken.
Pour the syrup over the top of the cake, sprinkle with orange zest and to with the remaining chocolate orange.