2. In a clean bowl whisk the egg whites until they are stiff, but not dry. Gradually whisk in the sugar a spoon at a time until it has all been incorporated and the mixture is no longer gritty.
3. Quickly whisk in the cornflour and vinegar, which you have mixed together into a paste, and then lightly fold in about three quarters of the pistachios.
4.Spoon the mixture onto the baking tray to make four round shells with a slight hollow in the middle for the filling. Then sprinkle over the remaining pistachio nuts, and bake low in the oven for about an hour, or until they are firm and crisp on the outside.
If they brown too quickly you may need to turn the oven down, or put the tray lower down in the oven. When they are cooked leave in the oven to cool - preferably overnight.
5. To make the granita, simply puree the fruit with the cordial and push through a fine mesh sieve. Add the lemon juice and then pour into a shallow container and freeze for about an hour. By this time the granita should be starting to freeze around the edges.
6. Gently stir the crystals with a fork and then put the container back into the freezer. Keep doing this every half hour, taking care not to crush the crystals too much otherwise you will lose the lovely 'grainy' texture.
When the mixture has reached the consistency of a firm slush it is ready to be eaten.
Finally, when you are ready, assemble the meringue with the cream and granita and serve straight away. I know I am definitely looking forward to a long, hot summer. It is the perfect excuse for eating lots more lovely meringue with refreshing fruit granita!