Preparing the Brownie Layer

1. Preheat your oven to 350°F (175°C). Line the bottom of a 9-inch springform pan with a piece of parchment paper.
2. In a medium mixing bowl, combine the brownie mix according to the package directions, along with the oil, eggs, and water specified on the box. Stir everything together until the batter is uniform and no dry spots remain.
3. Pour the prepared brownie batter into the parchment-lined springform pan and spread it out evenly. Bake in the preheated oven for about 30 to 35 minutes, or until the center appears set but still slightly soft and fudgy. Let the baked brownie cool completely in the pan.

Making the No-Bake Cheesecake

1. In a small, separate dish, combine the 1 tablespoon of cold water with the 1 teaspoon of gelatin powder. Sprinkle the gelatin over the surface of the water and let it sit undisturbed for a few minutes until it thickens and sets.
2. Carefully microwave the gelatin mixture for about 8 to 10 seconds until it becomes liquid again. Watch it closely to avoid overheating.
3. To whip the cream, place a metal mixing bowl and the whisk attachment (or beaters) into the freezer for 5 to 10 minutes to chill thoroughly.
4. Pour the very cold heavy whipping cream into the chilled bowl. Use an electric mixer on medium-high speed to beat the cream until it starts to thicken. Gradually add just 3 tablespoons of the dry brownie mix and the microwaved liquid gelatin, then continue beating on high speed until firm peaks form in the whipped cream. Set this whipped cream aside.
5. In a large bowl, beat the softened cream cheese on medium-high speed for 2 to 3 minutes until it is completely smooth and lump-free, pausing occasionally to scrape down the sides of the bowl. Next, add the granulated sugar and vanilla extract, beating until they are fully mixed in.
6. Now, add the remaining 2 cups of dry brownie mix to the cream cheese mixture. Beat for approximately 90 seconds, ensuring the brownie mix is thoroughly incorporated into the cheesecake base.
7. Finally, gently fold the prepared whipped cream into the brownie cheesecake batter until the mixture is well combined and uniform in color. Pour the cheesecake batter over the cooled brownie base in the springform pan. Cover the pan and refrigerate the cheesecake for at least 3 to 4 hours, or until fully set.

Adding the Finishing Touches

1. Prepare a second batch of whipped cream for the topping using the same method as described for the cheesecake filling (chilling the bowl, beating cream and powdered sugar).
2. If desired, transfer the whipped cream to a large piping bag fitted with an open star tip and pipe a decorative border around the edge of the set cheesecake. Finish by drizzling hot fudge sauce over the top.