Break 150 g Chocolate into chunks and put into a glass bowl over a pan of water. Simmer the water so that the chocolate melts. Take off the heat and stir in 1 teaspoon Vanilla extract.
Add 3 Egg white to a large mixing bowl. Whisk until stiff and peaks form when the whisk is removed. Add half of the 50 g Caster sugar and mix. Add the remaining sugar and mix again.
In a separate bowl add 100 ml Double (heavy) cream. Whisk until smooth and stiff.
Add a spoonful of the whisked egg to the melted chocolate and gently fold it in.
Add the folded chocolate mixture to the remaining egg white and fold it all together.
Add the whipped cream and gently fold in.
Divide between ramekins or small cups and refrigerate for 2 hours.
Notes
Make sure to gently heat the dark chocolate when you are melting it. You want the water to be barely simmering when the bowl of chocolate is over it. We wouldn't recommend using a microwave to melt the chocolate, as it can break and separate.
This is a great recipe to make if you have saved egg whites from making scrambled eggs. As the best scrambled eggs need extra yolks added to them.
You can serve this easy chocolate mousse recipe in pretty much anything, but keep in mind that the portions are small due to the intense flavour. We used little ramekins, but a tea cup or espresso cup would work. Or even a champagne glass if you want to be fancy.
For the perfect texture, you need to let the mousse sit in the fridge for at least 2 hours. Overnight is best though.
Make sure you allow the melted chocolate to cool a little before adding to the egg whites, as you don't want the eggs to cook.
You will need to fold, rather than stir, the ingredients in to ensure that you have a fluffy mousse.