Melt the Chocolate & Butter: Combine dark chocolate and unsalted butter in a heat-proof bowl over a double boiler, stirring until melted and smooth, about 5-7 minutes.

Whisk the Eggs and Sugar: In a separate bowl, whisk together eggs and granulated sugar until pale and fluffy, about 5 minutes.

Fold in the Chocolate Mixture: Once the chocolate mixture has cooled slightly, gently fold it into the egg mixture until combined.

Whip the Cream: In another bowl, whip heavy cream until stiff peaks form, taking about 3-4 minutes.

Combine Mixtures: Gently fold the whipped cream into the chocolate and egg mixture until fully incorporated.

Add Flavor: Stir in vanilla extract and a pinch of salt, then gently fold in raspberries.

Chill: Pour the mousse mixture into a prepared cake pan and refrigerate for at least 4 hours or overnight until set.

Serve: Once set, remove from the pan, slice into wedges, and garnish with extra raspberries.