Preheat the oven to 180 C. Butter one 23cm cheesecake tin or one with a removable base.
Combine the chocolate crumbs, softened butter, caster sugar and cinnamon. Mix well and press mixture into the buttered tin; set aside.
In a medium sized bowl beat the softened cream cheese until smooth. Gradually add caster sugar, mixing until well blended. Add eggs, one at a time. Beat at low speed until very smooth.
Melt the dark chocolate with cream in a bowl or pot set over boiling water. Stir until smooth.
Add chocolate mixture to cream cheese mixture and blend well. Stir in sour cream, salt, coffee, coffee liqueur and vanilla essence. Beat until smooth. Pour mixture into prepared tin.
Bake in the centre of preheated oven for 45 minutes. Do NOT overbake. Centre will be soft but will firm up when chilled. Leave cheesecake in the oven with the heat turned off and the door ajar for 45 minutes.
Remove cake from oven and chill for 12 hours. Just before serving, top cake with mounds of flavoured double cream and garnish with chocolate leaves.
To make the flavoured cream: Beat cream until soft peaks form, then beat in icing sugar and coffee liqueur.
To make chocolate leaves: Melt dark chocolate in a pan or bowl set over boiling water and stir until smooth. Brush real non-toxic plant leaves (such as orange leaves) on one side with melted chocolate. Freeze until firm and then peel off leaves. Freeze chocolate leaves until needed.