Prepare Pan and Crust: Preheat oven to 350°F (175°C). Line a 9x9 inch pan with parchment paper, leaving an overhang. Pulse cookies into fine crumbs in a food processor. Mix crumbs with melted butter until moistened. Press mixture firmly into the bottom of the prepared pan.

Mix Cake Batter: In a medium bowl, whisk together flour, sugar, cocoa powder, baking soda, and salt. In a larger bowl, whisk together the egg, oil, buttermilk, vinegar, and vanilla. Stir the red food coloring into the wet ingredients until uniform. Add the dry ingredients to the wet and whisk until just combined; do not overmix.

Bake and Cool Base: Pour the cake batter over the crust and spread evenly. Bake for 20-25 minutes, or until a skewer inserted into the center comes out clean. Let the pan cool completely on a wire rack.

Make Cheesecake Filling: In a large bowl, beat the 16 oz of softened cream cheese with an electric mixer until completely smooth. Add 1 cup of powdered sugar and 1 tsp of vanilla, and beat until combined and smooth. In a separate chilled bowl, whip the cold heavy cream until stiff peaks form.

Combine and Layer Cheesecake: Gently fold one-third of the whipped cream into the cream cheese mixture to lighten it. Then, fold in the remaining whipped cream until no streaks remain. Spoon the filling over the cooled cake layer and spread evenly. Cover and refrigerate for at least 6 hours, or preferably overnight, until firm.

Frost, Cut, and Serve: For the frosting, beat the 4 oz of cream cheese, 1 cup of powdered sugar, milk/cream, and 1/2 tsp of vanilla until smooth. Lift the chilled block from the pan using the parchment sling. Cut into 16 even squares, wiping the knife clean between cuts. Pipe or dollop frosting on each bite and garnish with mini chocolate chips or cake crumbs if desired. Serve chilled.