Preheat your oven to 375°F (190°C).

In a medium-sized saucepan over low heat, melt the dark chocolate chips and unsalted butter together, stirring gently until smooth. Remove from heat and let cool slightly.

In a large mixing bowl, whisk together the sugar, salt, and eggs until thick and pale, taking about 4-5 minutes.

Slowly add the melted chocolate mixture into the egg mixture, stirring continuously.

Gradually sift in the cocoa powder and add the vanilla extract, mixing until fully incorporated.

Grease an 8-inch round cake pan with butter and line the bottom with parchment paper.

Pour the batter into the prepared cake pan and smooth the top with a spatula.

Bake for about 25 minutes, or until the cake is set but still moist in the center.

Allow the cake to cool in the pan for about 10 minutes before inverting it onto a wire rack.

Dust with powdered sugar if desired.