Preparation method
Put the double cream in a small pan on a medium heat and leave to warm up.
Meanwhile, snap the chocolate up into small pieces. Once the cream is just starting to steam, remove it from the heat and add the chocolate. Don’t stir it (tempting though it is!) but just leave it to sit and melt for about 5 mins or so.
In the meantime, separate the eggs, putting the yolks in a mug or small bowl and the whites in a large spotlessly clean bowl (or the bowl of a freestanding electric mixer, if using).
Whisk the whites, preferably using a hand-held electric whisk (or the electric mixer) until they reach a medium peak. To test, stick the whisk into the egg white and then flip it handle side down. The peak should look like a floppy Noddy’s hat, not standing up straight to attention. If so, then add 1 tablespoon of the sugar and whisk it up again until the whites begin to become shiny. Then while continuing to whisk, add another tablespoon of the sugar. Make sure that the whites are whisked up well and all of the sugar is dissolved before whisking in the final tablespoon of sugar.
Meanwhile, have a look at the chocolate. It may not look like it, but the chocolate will most likely be melted by now, so stir everything together. Then add the egg yolks and stir to combine.
Once the whites are lovely and thick and glossy, stir in a spoonful of the chocolate mixture. This will loosen the whites up a bit and make it easier to manage the next step. Gradually pour all of the chocolate into the egg whites and then gently fold them together. Try not to be too heavy-handed or over mix this, as it is good to keep as much air as possible in it.
Divide between the four 150ml glasses or ramekins and lightly press the raspberries into the tops. Cover each one loosely with cling film and then pop in the fridge for 30 minutes or so to firm up (or if you want to eat them ASAP, put them in the freezer for 15 minutes). These can be made in the morning for a dinner party in the evening. If in the fridge for that long, I like to take them out 15 minutes or so before I need them so that they are not too cold for the guests.
Just before serving, decorate the top of the mousse with icing sugar. I hold a piece of paper with a straight edge quite closely over the part I don’t want the icing sugar to be on and then dust away (through a fine sieve) to give a nice detail over about a third of the top.