Step 1

Preheat oven to 350 degrees F (175 degrees C). In a large bowl, mix together the cookie crumbs, confectioners' sugar and 1/3 cup cocoa. Add melted butter and stir until well mixed. Pat into the bottom of a 9 inch springform pan. Bake in preheated oven for 10 minutes; set aside. Increase oven temperature to 450 degrees F (230 degrees C).

Step 2

In a large bowl, combine cream cheese, white sugar, 1/4 cup 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 sour cream and Irish cream liqueur; mixing on low speed. Pour filling over baked crust.

Step 3

Bake at 450 degrees F (230 degrees C) for 10 minutes. Reduce oven temperature to 250 degrees F (120 degrees C), and continue baking for 60 minutes.

Step 4

With a knife, loosen cake from rim of pan. Let cool, then remove the rim of pan. Chill before serving. If your cake cracks, a helpful tip is to dampen a spatula and smooth the top, then sprinkle with some chocolate wafer crumbs.