01 -
Carefully crack your eggs, separating the whites from the yolks. Place the whites in a large mixing bowl (you'll need space for them to expand when whipped) and the yolks in a smaller bowl. Set the whites aside for now - we'll come back to them shortly.
02 -
Give those egg yolks a good whisking until they're smooth and have a slightly lighter color. This helps them incorporate more easily into the other ingredients later.
03 -
Break the chocolate into smaller pieces and place them in a microwave-safe bowl along with the butter. Heat in 30-second bursts, stirring between each interval until completely melted and smooth. Be careful not to overheat! Let it cool slightly - we don't want it to scramble the eggs when they meet.
04 -
In another bowl, whip the cream until stiff peaks form - when you lift the beaters, the cream should hold its shape firmly. Keep a close eye on it as you're whipping; there's a fine line between perfectly whipped cream and accidentally making butter!
05 -
Return to your bowl of egg whites and add the caster sugar. Whip them until they form firm peaks - they should stand up straight with just a slight curl at the tip when you lift the beaters. The whites should look glossy and smooth.
06 -
Take your whisked egg yolks and gently fold them into the whipped cream using a large metal spoon or rubber spatula. Use a light hand and a figure-eight motion to maintain as much air as possible in the mixture. Next, pour in the cooled melted chocolate and continue folding until just combined and no streaks remain.
07 -
Now for the most delicate step - add one-third of the whipped egg whites to the chocolate mixture and fold gently to lighten it. Then add the remaining egg whites in two batches, folding with a light touch each time until everything is just combined. The mixture should look light, airy and uniform in color with no white streaks.
08 -
Divide your mousse mixture between serving glasses or ramekins. Cover each with plastic wrap (try not to let it touch the surface if you want a perfectly smooth top) and refrigerate for at least 6 hours or overnight. Patience is key for the mousse to set properly!
09 -
Just before serving, top each mousse with a generous dollop of freshly whipped cream and a sprinkle of chocolate shavings. For an extra touch, you could add a few fresh berries or a mint leaf for color.