• Preheat oven to 160°C (325°F).

For Crust:

• Put biscuits in food processor and blend until they resemble fine crumbs. Add cocoa and melted butter and mix well. Press into the bottom of a 9-inch springform pan.
• Bake for 5 to 8 minutes, until firm but not browned; cool.
• Raise oven temperature to 190°C (375°F).

For Filling:

• In a large bowl, beat cream cheese with an electric mixer until light and fluffy. Gradually add sugar, mixing well. Beat in cocoa. Add eggs, one at a time, beating well after each addition. Stir in coffee liqueur, coffee and vanilla. Pour into the cooled crust.
• Bake for about 30 minutes, or until the sides are set but there is a distinct jello-like wobble in the centre. Take the cheesecake out and place it on a wire rack.
• Raise temperature in oven to 220°C (425°F).

For Topping:

• Combine sour cream, 2 tablespoons sugar and vanilla in a small bowl; mix well. Spread evenly over the hot cheesecake. Bake for 5 to 7 minutes – don't overcook it - it will just start to lose itsshine and then firm up once chilled.
• Remove cheesecake from oven and cool to room temperature on a wire rack. Refrigerate, covered lightly with foil, for at least 8 hours or preferably overnight.
• Carefully remove cheesecake from pan and garnish with grated chocolate. Take out of the fridge about 20 minutes prior to serving.