Step 1: Preheat your oven to 350°F (175°C). Lightly grease a 9-inch springform pan. Line the bottom with parchment paper for easy removal.
Step 2: Press the entire roll of chocolate chip cookie dough evenly into the bottom of the prepared springform pan. Bake for 10-12 minutes, or until lightly golden. Remove from oven and let cool slightly while preparing the next layer.
Step 3: Prepare the brownie batter according to the package directions. Pour the brownie batter evenly over the partially baked cookie crust in the springform pan.
Step 4: In a large bowl, beat the softened cream cheese with granulated sugar until smooth and creamy. Beat in the all-purpose flour and vanilla extract until just combined.
Step 5: Add the eggs, one at a time, beating on low speed until just incorporated after each addition. Do not overmix. Gently fold in the sour cream until combined.
Step 6: Pour the cheesecake batter evenly over the brownie layer in the springform pan. Wrap the bottom of the springform pan tightly with aluminum foil to prevent water from seeping in if using a water bath.
Step 7: Place the springform pan into a larger roasting pan. Fill the roasting pan with hot water to about halfway up the sides of the springform pan. This is called a water bath (bain-marie) and helps prevent cracks.
Step 8: Bake for 60-75 minutes, or until the edges are set but the center still has a slight jiggle. Turn off the oven, crack the door open, and let the cheesecake cool in the oven for 1 hour. Remove from the water bath, remove foil, and transfer to a wire rack to cool completely at room temperature. Once cool, refrigerate for at least 4 hours, or preferably overnight, until thoroughly chilled and set.
Step 9: For the chocolate ganache: In a small saucepan, heat 1/2 cup heavy cream over medium heat until it just begins to simmer. Remove from heat and pour over the semi-sweet chocolate chips in a heatproof bowl. Let sit for 5 minutes, then whisk until smooth and glossy.
Step 10: Pour the cooled ganache over the chilled cheesecake, spreading evenly. Refrigerate for another 30 minutes to an hour to allow the ganache to set.
Step 11: For the whipped topping: In a cold bowl, combine 1 cup very cold heavy cream, 2 tablespoons powdered sugar, and 1/2 teaspoon vanilla extract. Beat with an electric mixer on high speed until stiff peaks form.
Step 12: Remove the cheesecake from the springform pan. Top the cheesecake with generous dollops of whipped cream. If desired, sprinkle with reserved cookie or brownie crumbles for garnish. Slice and serve immediately. Store leftovers in the refrigerator.