I got this recipe from CPIT when I trained their over 15 years ago, and I have been making it ever since. It is super rich, so only a small portion will do most people.
250ml whole milk
300g good quality 70% cocoa chocolate - I used Whittaker's
50g caster sugar
2 tablespoons Tia Maria liqueur
Separate the eggs and set the whites aside.
Hydrate the gelatine with a few tablespoons of cold water and set aside to swell.
Beat the yolks together with the caster sugar until the mixture is pale, light and fluffy.
At the same time heat the milk in a heavy based saucepan until it reaches boiling point.
Pour the milk into the yolks and whisk until combined. It is particularly important to add the milk to the yolks: done the other way around the eggs will cook and scramble.
Clean the bottom of the pot and transfer the eggs and milk back into the pot.
Using a spatula gently heat the mixture, stirring it constantly until it starts to thicken.
If you think its getting to hot too quickly take it from the heat for a minute or two and continue to stir. Don't allow the mixture to boil or the custard will curdle.
Once the custard coats the back of the spoon remove it from the heat and set aside.
Heat the gelatine and water in the microwave in short bursts until it is melted. Stir it into the custard.
Melt the chocolate. I usually do this in a Pyrex bowl in the microwave: put it on for 30 seconds, then stir and repeat once. Now stir until the last of the chocolate lumps have melted. Don't overheat or the chocolate will be ruined and don't have the chocolate too hot or it will spoil the custard.
Stir the melted chocolate and the Tia Maria into the custard and set aside to cool.
The mixture needs to cool until it is at room temperature.
Beat the eggs whites until soft peaks form and transfer them to another bowl.
The whites must be beaten in a spotlessly clean bowl or they will not reach their full volume. That's why I beat then first: otherwise I would need to thoroughly clean the bowl after beating the cream.
Now fold the egg whites into the chocolate mixture a third at a time. They need to be thoroughly mixed without losing too much of the air the egg whites bring to the mixture.
Pour the mousse into a serving bowl, cover with food wrap and refrigerate for at least a few hours before serving.
I put ours into one big bowl, but it looks equally good in individual serving dishes.
Though it's quite an involved recipe, it is definitely worth the effort. Happy cooking Emily. I'm sure your flat mates will love you for making this one.