Let’s assemble this decadent dessert layer by layer:

1. Make and Bake the Brownie Base:

Preheat oven to 350°F (175°C). Line the bottom of a 9-inch springform pan with parchment paper.

In a medium bowl, combine the brownie mix, melted butter, eggs, and 2 tablespoons water. Stir until just combined (follow specific mix instructions if drastically different).

Pour the batter into the prepared springform pan and spread evenly.

Bake for 20-24 minutes, or until a toothpick inserted into the center comes out clean or with moist crumbs (for a fudgy texture, slightly underbaking is often good).

Allow the brownie to cool completely in the pan on a wire rack.

2. Prepare Gelatin (Batch 1 – for Chocolate):

While brownie cools, start mousse prep. In a small dish, sprinkle 1 teaspoon of gelatin over 1 tablespoon of cold water. Let stand 1 minute to bloom.

3. Melt Chocolate Component:

In a separate microwave-safe bowl, combine the mini chocolate chips and 1 tablespoon of heavy whipping cream.

Microwave in 30-second increments at 50% power, stirring after each, until the chocolate is melted and smooth.

Gently microwave the bloomed gelatin (from step 2) for 8-10 seconds until it turns back into a liquid. Do not boil.

Pour the liquid gelatin into the melted chocolate mixture and stir quickly to combine. Set aside to cool slightly.

4. Prepare Gelatin (Batch 2 – for Whipped Cream):

Place a medium-sized metal mixing bowl (and beaters, if possible) in the freezer for 5-10 minutes to chill.

In another small dish, sprinkle the remaining 1 teaspoon of gelatin over the remaining 1 tablespoon of cold water. Let stand 1 minute to bloom.

5. Make Stabilized Whipped Cream:

Pour 1 cup of cold heavy whipping cream into the chilled mixing bowl. Beat with an electric mixer on medium-high speed until it starts to thicken.

Gently microwave the second batch of bloomed gelatin (from step 6) for 8-10 seconds until liquid.

With the mixer on low speed, slowly pour the liquid gelatin into the thickening heavy cream.

As the cream continues to thicken, gradually add the 3 tablespoons of powdered sugar. Continue beating on high speed until stiff peaks form. Set this stabilized whipped cream aside briefly.

6. Make Cream Cheese Base:

In a separate large bowl (or the cleaned bowl of your stand mixer), beat the softened cream cheese on medium-high speed for 2-3 minutes, until completely smooth. Scrape the bowl occasionally.

Add the granulated sugar and beat until well combined.

Add the cocoa powder and beat until well combined, scraping down the bowl occasionally.

Slowly add the remaining 2 tablespoons of heavy whipping cream and the teaspoon of vanilla extract. Continue beating until combined.

7. Combine Mousse Components:

Add the slightly cooled melted chocolate/gelatin mixture (from step 3) to the cream cheese mixture. Mix thoroughly until well combined.

Finally, gently fold the prepared stabilized whipped cream (from step 5) into the chocolate cream cheese mixture using a rubber spatula until evenly combined and no streaks remain. Do not stir vigorously; maintain the airiness.

8. Assemble Mousse Layer:

Line the sides of the springform pan (containing the cooled brownie) with parchment paper or a cake collar, if desired (this helps removal).

Pour the finished chocolate mousse batter over the top of the cooled brownie base. Spread evenly.

9. Chill Thoroughly:

Refrigerate the cake, covered loosely, for at least 4 hours, or preferably overnight, until the mousse is completely firm and set.

10. Make Topping:

Prior to serving, prepare the whipped cream topping. Place another medium-sized metal mixing bowl (and beaters) in the freezer for 5-10 minutes to chill.

Pour the ¾ cup heavy whipping cream into the chilled bowl. Beat on medium-high speed until it starts to thicken.

As the cream thickens, add the 3 tablespoons of powdered sugar. Continue beating on high speed until stiff peaks form.

11. Decorate and Serve:

Carefully run a thin knife or offset spatula around the edge of the cheesecake to loosen it from the sides of the springform pan (remove parchment/collar if used). Release and remove the side ring.

Transfer the whipped cream topping to a piping bag fitted with a large open star tip (like #1M or similar). Pipe a decorative border around the top edge of the cake.

Drizzle the top with warmed hot fudge sauce.

Sprinkle with additional mini chocolate chips.

Serve immediately or keep refrigerated until serving. Slice with a sharp knife dipped in hot water