Step 1: Preheat oven to 350°F (175°C). In a medium bowl, combine finely crushed chocolate sandwich cookies and melted butter until well mixed. Press firmly and evenly into the bottom of a 9-inch springform pan. Bake for 8-10 minutes, then remove and let cool completely on a wire rack.
Step 2: Reduce oven temperature to 325°F (160°C). Prepare the brownie mix according to package directions. Pour the brownie batter evenly over the cooled cookie crust in the springform pan. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs. Let cool completely on a wire rack.
Step 3: While the brownie cools, prepare the cheesecake layer. In a large bowl, using an electric mixer, beat the softened cream cheese and 1/2 cup granulated sugar until smooth and creamy. Beat in the eggs one at a time, mixing just until combined after each addition. Stir in 1 teaspoon vanilla extract. Pour the cheesecake mixture over the cooled brownie layer.
Step 4: Bake the cheesecake at 325°F (160°C) for 45-55 minutes, or until the edges are set and the center slightly jiggles when gently shaken. Turn off the oven, prop the door open slightly, and leave the cheesecake inside for 1 hour to cool gradually. Remove from oven, cool completely on a wire rack, then chill in the refrigerator for at least 4 hours, or preferably overnight.
Step 5: Prepare the edible cookie dough layer. In a medium bowl, cream together 1/2 cup softened butter, 1/4 cup granulated sugar, and 1/2 cup brown sugar until light and fluffy. Beat in 1 teaspoon vanilla extract and 1/4 teaspoon salt. Gradually mix in the heat-treated flour until just combined. Add milk or cream, one tablespoon at a time, until the desired soft cookie dough consistency is reached. Fold in the mini chocolate chips. Spread this edible cookie dough evenly over the chilled cheesecake layer.
Step 6: Make the chocolate ganache topping. In a small saucepan, heat 1 cup heavy cream over medium heat until it just begins to simmer around the edges. Remove from heat and pour the hot cream over 1 cup semi-sweet chocolate chips in a heatproof bowl. Let stand for 5 minutes without stirring, then whisk until smooth and glossy. Let the ganache cool for 10-15 minutes, stirring occasionally, until it's slightly thickened but still pourable.
Step 7: Pour the slightly cooled ganache evenly over the edible cookie dough layer. Return the cheesecake to the refrigerator and chill for at least 2 more hours, or until the ganache is set.
Step 8: To serve, carefully run a thin knife around the edge of the springform pan before releasing and removing the sides. For clean slices, dip a sharp, thin knife into hot water, wipe it clean, and cut. Clean the knife between each slice. Serve chilled and enjoy! (See notes for heat-treating flour instructions).