1: Using the back of a wooden spoon, press 100g raspberries through a sieve into a bowl; discard the seeds. Add 2 tbsp icing sugar to the juice and mix until smooth.
2: Preheat the oven to gas 2, 150°C, fan 130°C. Put the egg whites in the bowl of a freestanding electric mixer and whisk to stiff peaks (alternatively, use an electric hand whisk). Gradually add the caster sugar, a dessert spoon at a time, and continue whisking for about 10 mins, until the mixture is thick and glossy. Fold in 1 tsp vanilla extract. Swirl in 1 tbsp of the raspberry mixture (reserve the rest for later).
3: Using 2 large spoons, heap the mixture onto a baking tray in 6 evenly sized dollops, spacing them well apart. Scatter each one with the pistachios, reserving a little to garnish.
4: Reduce the oven temperature to 110°C, fan 90°C, gas 1/4. Cook, on the middle shelf, for 1 hour, 45 mins. Remove the tray from the oven, drizzle a little more of the raspberry mixture over the meringues and then continue cooking for a further 15 mins. They should be crisp and sound hollow when the bottoms are tapped. Turn off the oven and leave the door slightly ajar. Leave the meringues to cool inside.
5: Whip the cream to soft peaks, then fold in the remaining icing sugar and vanilla extract. Serve the meringues with a dollop of vanilla cream, a drizzle of the remaining raspberry mixture and the pistachios. Garnish with the remaining fresh raspberries.