01 - Preheat oven to 350°F. Grease an 8-inch round springform pan and line the bottom with parchment paper.
02 - Melt chocolate and butter together in a heatproof bowl set over gently simmering water, stirring until smooth. Remove from heat and let cool slightly.
03 - Whisk granulated sugar and sea salt into the melted chocolate and butter mixture until well combined.
04 - Beat in the eggs one at a time, whisking thoroughly after each addition. Stir in vanilla extract until the batter is glossy and thick.
05 - Pour batter into prepared pan and smooth the top evenly with a spatula.
06 - Bake for 25 to 30 minutes, until edges are set but the center remains slightly soft. A toothpick inserted should have a few moist crumbs attached.
07 - Allow cake to cool completely in the pan on a wire rack. Once cooled, remove from pan and place on serving plate.
08 - Top with fresh raspberries and dust lightly with icing sugar if desired. Serve at room temperature.