Melt chocolate in microwave on medium for 30 seconds, then stir and zap for another 20 seconds and keep stirring until melted and smooth. Set aside to cool slightly.

Place eggs and sugar or natvia in a medium bowl and beat with electric beaters on high for 5 minutes, or until mixture is pale, thick and roughly doubled in volume. Fold in cooled chocolate until combined, but do not overwork.

In a separate bowl, whip cream until thickened (be careful not to over-beat). Carefully fold the cream into the chocolate mixture, trying to keep the mixture as light as possible.

Divide raspberries between your four serving glasses or tea cups. Spoon mousse over the top and sprinkle generously with chopped pistachios. Chill in fridge for at least 1 hour.