Melt chocolate in a double boiler until smooth, then let cool slightly

Whisk egg yolks with cognac until pale and creamy

Gradually fold the melted chocolate into the egg yolk mixture

In a clean bowl, whisk egg whites with salt until soft peaks form, gradually add sugar until stiff peaks form

Whip cream to soft peaks in another bowl

Gently fold one-third of egg whites into chocolate mixture to lighten

Fold in remaining egg whites in two additions, being careful not to deflate

Fold in whipped cream until just combined

Divide among serving glasses and refrigerate for at least 2 hours before serving

Garnish with fresh berries just before serving