Preheat your oven to 350°F (175°C). Line the bottom of an 8-inch round cake pan with parchment paper. Lightly grease the sides with butter to prevent sticking and ensure easy removal after baking.

Place the chopped dark chocolate and butter in a heatproof bowl. Set the bowl over a saucepan of gently simmering water. Stir occasionally until the mixture becomes smooth and glossy, then remove from heat and let it cool slightly.

Whisk the granulated sugar into the warm chocolate mixture until well combined. Add the eggs one at a time, whisking thoroughly after each addition. This step creates a smooth and velvety batter with a rich texture.

Sift the cocoa powder and salt over the batter. Add the vanilla extract. Gently fold everything together using a rubber spatula until fully combined. Avoid overmixing to maintain the cake’s delicate and fudgy consistency.

Pour the batter into the prepared cake pan and smooth the top. Bake in the preheated oven for about 25 to 30 minutes. The edges should be set while the center remains slightly soft.

Allow the cake to cool in the pan for 10 minutes, then carefully transfer it to a cooling rack. Once completely cooled, dust with powdered sugar and garnish with fresh berries before slicing and serving.