1. Separate 4 egg yolks from the egg whites, keep the egg yolks and egg whites in separate bowls.
2. Beat the 4 egg whites with a whisk or electric mixer until egg whites turn into pure white and stiff peaks have formed. Add 100g of icing sugar and continue beating until consistency has thickened.
3. Put the bar of chocolate in a pan broken into pieces and add a tablespoon of water.
   Melt the chocolate in the pan on a very low heat over a hob, stirring occasionally with a wooden spoon (preferably).
4. Once chocolate has melted, remove the pan from the heat and add the 4 egg yolks and immediately whisk very rapidly until egg yolks have mixed thoroughly with the melted chocolate.  (It is important to whisk as rapidly as possible so as to not allow the egg yolks to cook in the heat of the melted chocolate.)
5. In a large mixing bowl, fold together or stir GENTLY the contents of the whisked egg whites and the melted chocolate using a wooden spoon or spatula until mixed together thoroughly. (It is important not to whisk or stir violently these two mixtures together as this will result in air escaping from the egg whites and mousse will lose a lot of texture.)
6. Pour the mousse into ramekins or similar sized containers and let them set in the fridge for at least 1 hour before serving.

Tip: These mousses need to be kept refrigerated as they contain eggs and should keep in the fridge for about 3 days.

As an extra touch you could also add toasted flaked almonds to the top of the mousse before serving.