Combine wafer crumbs, 1/2 cup (125 mL) cocoa, icing sugar and butter (can be mixed in the food processor to save some time).
Press over bottom and 2 inches (5 cm) up the sides of a 9-inch (23 cm) springform pan; set aside.
Beat cream cheese until smooth in a large bowl. Gradually beat in granulated sugar, 2 tbsp (30 mL) cocoa and vanilla extract. Add eggs, one at a time, beating well after each addition. Stir in cream and whiskey.
Pour into prepared crust; set on baking sheet. Bake in preheated 375 ºF (190 ºC) oven 50 to 55 minutes.
Cool then chill. Drizzle melted chocolate over surface of cake before serving.