Slowly melt the chocolate in a heat-proof basin over a pan of shimmering water. (see advice about water and chocolate above). This can take up to 6 minutes.
Once melted, take off the heat and stir so that it’s smooth and glossy.
Set to one side for 2-3 minutes to cool.
Whisk the egg yolks for about 1 minute, then add half the grated zest and all the juice of the orange for a further minute.
Add to the egg yolk mixture a third if the sugar, and whisk, then the next third and whisk and then the final third and whisk (if adding Cointreau you can do so now).
Whisk the egg whites until stiff (i.e., the egg whites don’t slide out of the bowl if you turn the bowl upside down!).
Using a metal spoon fold the melted chocolate gently into the egg yolk mixture – a little at a time. Then fold in gently the egg yolks. This may take some time as you need to do this very carefully and slowly as you don’t want to lose the air out of the mixture. It will also take time to incorporate so don’t loose heart. It will finally all come together as a lovely goo!
Divide the raspberries between the dessert glasses, keeping some back for decoration.
Pour the chocolate mixture over the raspberries and cover with clingfilm. Leave in the fridge for about 3 hours to set.
Just before serving, remove cling film and decorate the top with some raspberries, grated zest of orange, sieved icing sugar and cream.
Make sure that when melting the chocolate over the simmering water that none of the water splashes onto the bowl. The general advice about melting chocolate is, make sure that the bowl doesn't touch the simmering water. I would go further - make sure that the water doesn't splash onto the bowl. This has happened to me. It makes the chocolate bitter and thus destroys the taste of this dish.
Recipe by Doe's Kitchen at http://doeskitchen.com/raspberry-and-orange-chocolate-mousse/