Preheat your oven to 350°F (175°C). Grease an 8-inch springform pan and line the bottom with parchment paper for easy release.

Melt 6 ounces of unsweetened chocolate with ½ cup of unsalted butter in a medium saucepan over medium-low heat until smooth.

Stir in 1 cup of granulated sugar, cool slightly, then add 3 large eggs and 1 tablespoon of pure vanilla extract, mixing until smooth.

Fold in 1 cup of all-purpose flour, 3 tablespoons of Dutch-process cocoa powder, and ½ teaspoon of salt until just combined.

Pour into the prepared pan and bake for 20-25 minutes, or until a toothpick inserted comes out with a few moist crumbs. Let cool completely in the pan.

Dissolve ¾ teaspoon of gelatin powder in 1 tablespoon of water and set aside to bloom.

In a small saucepan, heat ¾ cup of heavy cream with 2 tablespoons of sugar until simmering; remove heat and stir in bloomed gelatin until dissolved.

Pour hot mixture over 6 ounces of chopped semisweet chocolate, whisk until smooth, then cool to room temperature.

Whip remaining ¾ cup of heavy cream to medium-stiff peaks, fold in 1/3 into the chocolate mixture then fold in the rest.

Spread mousse over cooled brownie base and refrigerate for at least 2 hours.

Heat ¾ cup of heavy cream and 1 tablespoon of unsalted butter in a saucepan over medium heat until boiling.

Pour hot mixture over 9 ounces of chopped semisweet chocolate, let sit for a minute, then stir until smooth.

Allow ganache to cool at room temperature until thickened, about 15-20 minutes, stirring occasionally.

Spread ganache over the chilled mousse layer to create an even top.

Chill layered cake for an additional hour or until set, then carefully remove the sides of the springform pan.

Slice and serve your decadent Triple Chocolate Mousse Cake with optional fresh whipped cream or berries.