Mix crumbs, butter, and sugar. Press onto bottom and up the sides partway of a 23 cm springform pan. Freeze 5 minutes, then bake at 180ºC for ten minutes and allow to cool. Heat in a bowl or pan over boiling water half cup chocolate chunks until melted and smooth. Add quarter cup whipping cream and quarter cup Kahlua and stir until blended. In another bowl, beat cream cheese and sugar until fluffy. Add first mixture to the second and blend well. Add eggs one at a time, mixing well after each addition, and vanilla. Pour over prepared crust and bake 10 minutes at 200ºC . Decrease to 140ºC and bake another 45 minutes. Remove from oven to cool: loosen cake from rim of pan and remove. Melt remaining chocolate. Then add quarter cup whipping cream and the 2 Tablespoon Kahlua, mixing well. Spread on top of cake and refrigerate six or so hours. Before serving, beat remaining whipping cream with the powdered sugar and garnish cake by pipping it on (personally, I'll probably skip this step) and decorating with a few remaining chocolate chips (the picture of this is great!). Refrigerate leftovers.