01 - Preheat oven to 320°F. Grease an 8-inch round cake pan and line the bottom with parchment paper.
02 - In a heatproof bowl set over simmering water, melt dark chocolate and butter together, stirring until smooth. Remove from heat and allow to cool slightly.
03 - Stir in granulated sugar and vanilla extract until fully combined.
04 - Add eggs one at a time, mixing thoroughly after each addition.
05 - Gently fold in the heavy cream until the batter is smooth and glossy.
06 - Pour the batter into the prepared pan and smooth the surface evenly.
07 - Bake for 30 minutes or until the center is just set yet remains slightly soft.
08 - Let the cake cool in the pan for 10 minutes, run a knife around the edges, then remove carefully. Cool completely before chilling at least 1 hour for optimal texture.
09 - Dust with cocoa powder and serve with fresh raspberries or whipped cream as desired.