• Pre-heat your oven to 140C Fan/160C/325F/Gas Mark 3

For the base

• Crush the digestive biscuits in a bowl with the end of a rolling pin. You can also whizz them into crumbs using a food processor if you have one
• Melt the butter in a pan on a low heat
• Mix the butter and crushed biscuits together and press them into a 24cm springform cake tin

For the cheesecake filling

• In a bowl over some heated water melt the dark chocolate, set aside
• Mix together the cream cheese, eggs and caster sugar with a whisk until smooth
• Add the double cream and mix it in
• Add the melted dark chocolate, orange liquor and the zest and juice of the orange and mix until smooth
• Pour the mixture into the tin over the biscuit base and bake for 45 minutes
• Let it cool completely, and put in it the fridge to chill

For the buttercream and decoration

• Mix the butter, cocoa powder, icing sugar and orange liquor together until smooth
• Pipe swirls onto the cheesecake and add slices of Terry's Chocolate Orange to decorate