Preheat the oven to 325ºF and lightly grease an 8-inch springform pan or a cake pan with a removeable bottom. Line with parchment paper and grease the paper. Set the pan on a rimmed baking sheet.

Prepare the brownie batter according to the directions and spread in the prepared baking pan. Bake 20 to 25 minutes, or until the edges are set but the center is still a little jiggly. Remove and let cool completely.

In a large microwave safe bowl, melt the chocolate with the butter on high in 30 second increments, stirring in between until smooth.

Place the water in a small saucepan and sprinkle the gelatin over top. Let bloom 5 minutes, then place the pan over medium low heat and add ¼ cup of the heavy cream. Stir until the gelatin is dissolved, but do not let it come to a boil. Slowly whisk into the chocolate mixture.

In a large bowl, beat the remaining cream with the sweetener and vanilla extract until it holds stiff peaks. Stir about ¼ of the whipped cream into the chocolate to lighten it, then fold in the remaining cream until smooth.

Spread this mixture over the cooled cake and refrigerate while making the espresso mousse.

In the same saucepan as above, place the espresso. Sprinkle with the gelatin and let bloom 5 minutes, then place over medium low heat. Stir until the gelatin is dissolved, but do not let it come to a boil. Remove from heat and cool to lukewarm.

In a large bowl, beat the cream with the sweetener and vanilla extract until it holds stiff peaks. Gently fold in the cooled espresso mixture until well combined.

Spread over the chocolate mousse in the pan and refrigerate until firm to the touch, 1 to 2 hours.

Use a sifter to sprinkle the top of the cake evenly with cocoa powder.

Warm up a small sharp knife by either running boiling water over it or holding it over a gas flame for a few seconds. Run the knife around the inside of the pan to loosen the cake.

Release the pan sides for a springform pan. If using a cake pan with a removeable bottom, simply push the bottom up to release the cake.

Serve with fresh berries.