200g dark chocolate, broken into pieces
3 large eggs, separated
50g caster sugar
whipped cream, to serve (optional)
Place the chocolate and 120ml of water in a large heatproof bowl set over a pan of just simmering water – don’t let the bottom of the bowl touch the water. Heat gently, stirring regularly, until all of the chocolate has melted.
Remove from the heat and leave to cool slightly, then stir in the egg yolks with a wooden spoon until well combined.
In a large bowl, whisk the egg whites with the sugar until stiff peaks form, then gently fold them into the chocolate mixture.
Spoon the mousse into individual dishes and chill for at least 2 hours or overnight, if possible. To serve, top with whipped cream, if desired.