To make the base, mix together the crushed biscuits, hazelnuts, cinnamon and melted butter. Press evenly into a cake tin and chill to set. Meanwhile, start the filling by melting the chocolate and allow to cool down slightly. In a medium sized bowl mix together the cream cheese, eggs, orange zest and vanilla extract till smooth using an electric beater. Whilst still beating pour in the melted chocolate and beat till all streaks are gone. Spoon the filling into the prepared biscuit base and even out. Place the cheesecake into a larger dish and half fill around with hot water (Baine Marie) and bake in the oven at 150`c for approximately 50 minutes. Meanwhile make the frosting by beating together the white margarine, icing sugar and vanilla till light. Mix in the cheese, followed by the Irish cream. Place the cheesecake onto a serving dish and decoratively pipe the frosting on top. Arrange the chocolate shavings and hazelnuts on top and chill before serving.