Place the egg yolks and sugar in the bowl of a stand mixer fitted with a whisk attachment.
Whisk the eggs and sugar together for 8-10 minutes until voluminous and pale yellow. Scrape the bowl down with a rubber spatula every 2-3 minutes to make sure the eggs are well incorporated.
Break the chocolate up and place in a glass bowl. Place over a pot of barely simmering water and melt.
Once completely melted, remove from the heat and allow to cool down for 5 minutes.
In another clean bowl, whip the egg whites with a pinch of salt until stiff peaks form.
Whip the cold cream until firm peaks form.
Once the egg yolks are whipped, pour in the cooled chocolate and mix until combined. The mixture will stiffen up quite a bit, but that's fine.
Stir in one third of the cream to loosen the chocolate then gently fold in the remaining cream with a metal spoon.
Fold in the beaten egg whites, taking care not to lose the airy texture.
Transfer the chocolate mousse to a serving dish or individual glasses then place in the fridge. Allow to set for at least 6 hours but ideally overnight.
Top the chocolate mousse with whipped cream and fresh raspberries then serve.