Make the Crust: Preheat oven to 350 degrees F. Grease a 9-inch springform pan.
Blend the cookies and sugar together in a food processor until the cookies are finely ground. Add the melted butter and process until the crumbs are evenly moistened. Press the crumb mixture evenly onto the bottom of the prepared pan. Bake for 8 minutes. Remove from the oven and set on a wire rack while preparing the filling.
Make the Filling: Blend the cream cheese, sugar and cocoa powder in the food processor until smooth, scraping down the sides of the bowl as needed, about 30 seconds. Add the eggs one at a time, blending for 10 seconds each. Add the melted chocolate and blend to combine, scraping down the sides of the bowl once. Pour the filling into the crust and smooth the top.
Bake the cheesecake until the center is just set and the top looks dry, 1 hour to 1 hour 10 minutes. Cool on a wire rack for 5 minutes. Run a thin knife around the sides of the pan. Place the cake in the refrigerator, uncovered, for at least 8 hours, or overnight.
Make the Topping: Stir the cream, chocolate and sugar in a medium saucepan over low heat until the chocolate is completely melted and the mixture is smooth. Cool until slightly warm and pour over the center of the cheesecake, spreading to within ½-inch of the edge. Chill for at least 1 hour.
Run a thin knife around the sides of the pan and remove the pan sides. Transfer the cheesecake to a serving platter. Let stand for 2 hours at room temperature before serving. The cheesecake can be prepared up to 3 days in advance; cover with foil and store in the refrigerator.