Using the back of a wooden spoon press 100g/4oz blackberries through a sieve into a bowl, discarding the seeds. Add 2 tbsp icing sugar to the juice and mix until smooth.

Pre-heat oven to 150°C, 300°F, Gas Mark 2.

Put the egg whites in a bowl and whisk to stiff peaks using a hand held mixer. Gradually add the caster sugar with a dessert spoon and continue whisking for about 10 minutes, until the mixture is thick and glossy. Fold in 1 tsp of vanilla extract. Swirl in 1 tbsp of the blackberry mixture, saving the rest for later.

Using 2 large spoons, heap the mixture onto a greased baking tray into 6 evenly sized dollops, spacing them well apart, scatter each one with some of the crushed pistachios reserving a little to garnish.

Reduce the oven temperature to 110°C, 225°F, Gas Mark ¼ . Cook on the middle shelf for 1 hour 45 minutes. Remove the tray and drizzle a little of the blackberry juice over each meringue, and continue cooking for another 15 minutes. 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 inside to cool.

Whip the cream to soft peaks then fold in the remaining icing sugar and vanilla extract. Serve the meringues with a dollop of the cream, a drizzle of the remaining blackberry juice and a sprinkle of pistachios. Garnish with the remaining fresh blackberries.