Preparation / Directions:
In the 4 1/2-quart bowl of a heavy-duty electric mixer using the paddle attachment, beat the cream cheese at low speed for 30 to 45 seconds, until creamy. Gradually add the sugar in a steady stream and beat at medium speed until blended. At low speed, one at a time, add the eggs, beating well after each addition. Slowly beat in the reserved 2 cups of chocolate ganache. Beat in the cornstarch mixture. Pour the filling into the prepared pan and, using a rubber spatula, smooth the top. Bake the cheesecake for 1 hour and 15 minutes to 1 hour and 20 minutes, or until the center is set. (There will probably be cracks in the top of the cheesecake; they will shrink as the cheesecake cools and then will be covered with the ganache frosting.) Turn off the oven. Prop open the oven door with a wooden spoon and allow the cheesecake to cool in the oven for an hour. Set the cheesecake in the pan on a wire rack and cool completely.
Make the chocolate truffles: Transfer the chilled 1 cup ganache to a pastry bag fitted with a 1/2-inch plain tip (such as Ateco #6). Pipe l-inch mounds with pointed peaks onto a clean baking sheet. Refrigerate or freeze the truffles for 15 to 20 minutes, or until just firm enough to roll. Sift a light dusting of confectioners' sugar over the truffles. Lightly coat your palms and fingertips with confectioners' sugar. With your fingertips, pinch a truffle into a round, then roll it gently between your palms into a round ball. Place the truffle on the baking sheet, and form the remaining truffles into rounds. Refrigerate or freeze for about 10 minutes, just until firm. Roll the truffles in sifted cocoa powder to coat. Refrigerate.
Decorate the cheesecake: Run a thin-bladed knife around the edge of the cheesecake to loosen it from the side of the springform pan. Remove the side of the pan. Slide two metal cake spatulas under the cheesecake and transfer it to a serving platter. Using a metal cake spatula, spread the reserved room-temperature chocolate ganache evenly over the top and sides of the cheesecake. Place the chocolate truffles around the outside edge of the top of the cheesecake, spacing them evenly. Melt the white chocolate according to the instructions in the Chocolate Key. Using a fork, drizzle/shake the warm white chocolate in a decorative zigzag pattern over the top of the cheesecake. Refrigerate the cheesecake for at least 6 hours, or overnight, before serving. (The cheesecake can be prepared ahead and refrigerated for up to 5 days.) Remove the cheesecake from the refrigerator 30 minutes before serving. With a sharp, thin-bladed knife, cut the cheesecake into 12 truffle-topped slices, dipping the blade in hot water and wiping it dry after each sl