Break the chocolate into small pieces and add to a Pyrex bowl. Add the 120ml water to the bowl.
200 g dark chocolate, 120 ml water
Place a pan of water over a high heat and bring up to a simmer. Adjust the heat to maintain a simmer.
Place the chocolate bowl over the simmering water making sure it does not touch the water. Melt the chocolate slowly, stirring continuously.
Remove the chocolate and water mixture from the heat and place on a heatproof mat/towel to cool a little.
Stir the egg yolks into the chocolate with a spatula/wooden spoon until thoroughly combined.
3 large eggs
In a separate bowl, add the egg whites and the sugar and whisk until stiff peaks are achieved. I recommend using an electric hand whisk.
3 large eggs, 50 g caster sugar
When ready, very gently add the egg whites to the chocolate mixture and fold in. Be as gentle as possible as you want to encourage the air into the mix to make the mousse light and fluffy.
Gently spoon the mousse mixture into the serving bowls/dishes/terrines etc and place in the fridge to chill for at least a few hours but ideally overnight.