Brownie Cake:
Preheat the oven to 350℉. Grease and line a 9″ round springform pan with nonstick spray and parchment paper.
In a microwave-safe bowl, melt butter and chopped chocolate in 30-second intervals, stirring until smooth. Set aside.
In another bowl, whisk together flour, cocoa powder, and salt.
In a large mixing bowl, whisk sugars and eggs for 3 minutes until frothy.
Pour in the cooled chocolate mixture and whisk until combined.
Sift in dry ingredients and fold with a spatula until just combined.
Scrape batter into the prepared pan and bake for 25-30 minutes. Cool completely.
Raspberry Mousse:
Puree the raspberries and pass through a fine mesh sieve into a saucepan.
Sprinkle gelatin over water in a small bowl, allowing it to bloom for 5 minutes.
Heat raspberry puree over medium heat and dissolve the sugar. Remove from heat and stir in the gelatin mixture.
Transfer raspberry mixture to a shallow bowl and let it cool to room temperature.
In a stand mixer, whip cold cream and powdered sugar until stiff peaks form.
Fold in raspberry puree in two batches. Spread the mousse over the cooled brownie cake. Refrigerate for 4 hours or overnight.
Chocolate Ganache Glaze:
Place chopped chocolate in a heat-proof bowl.
Heat the heavy cream until it steams, then pour over the chocolate. Let it stand for 1 minute, then stir until smooth.
Let the ganache cool for 10 minutes until pourable.
Remove the cake from the pan, peel off the parchment, and place it on a wire rack.
Pour the ganache over the cake, covering the sides. Let it set, then transfer to a serving platter.
Top with fresh raspberries. Slice and serve.