Chocolate Orange Cheese cake

Ingredients
Base (personally doubled all these and made a thicker base)
4 tbsp butter, melted
115g/4oz digestive biscuits, finely crushed
2 tsp unsweetened cocoa powder

Chocolate Layer
800g/1lb mascarpone cheese
200g/7oz icing sugar
juice of 1/2 orange
finely grated rind of 1 orange
175g/6oz dark chocolate, melted

1. Grease an 8inch loose-bottomed cake tin.
2. To make the base, put the crushed biscuits, cocoa powder and melted butter in a large bowl and mix well. Press evenly onto base of tin.
3. Put the mascarpone and icing sugar into a bowl and stir in orange juice and rind. Add the melted chocolate and mix together until thoroughly combined.
4. Spread over base and chill in fridge for at least 4 hrs.