Preheat oven to 350°F In a large bowl, mix together the cookie crumbs, confectioner's sugar and 5 tablespoons cocoa. Add melted butter and stir until well mixed.
Pat into the bottom of a 9in loose-bottomed or springform cake tin. Bake in preheated oven for 10 minutes; set aside. Increase oven temperature to 450°F.
In a large bowl, combine cream cheese, superfine sugar, 4 tablespoons cocoa and flour. Beat at medium speed until well blended and smooth. Add eggs one at a time, mixing well after each addition. Blend in the soured cream and Baileys liqueur; mixing on low speed. Pour filling over biscuit base.
Bake at 450F for 10 minutes. Reduce oven temperature to 200F and continue baking for 60 minutes.
With a knife, loosen cake from sides of tin. Allow to cool slightly, then push up base of the tin to remove cheesecake. Chill before serving. If your cake cracks, a helpful tip is to dampen a palette knife and smooth the top, then sprinkle with some cookie crumbs.