Let’s make the meringues first. Preheat the oven to 140°C/Fan 120°C/Gas. Draw a 20cm circle on a sheet of baking parchment.
In a bowl, whisk the egg whites until they form stiff peaks. Add the sugar a spoonful at a time, whisking until you have a stiff and glossy meringue. Then, whisk in the cornflour and vinegar until combined. Swirl the pistachios through your meringue.
Carefully spoon the meringue onto the circle on the baking parchment, and use a palette knife to flatten to top. Bake for 1 hour, then turn the oven off and leave the meringue inside for at least 2 hours to dry out as it cools.
Now for the mulled pears. Pour the wine and water into a pan. Add all the other ingredients, except the pears and blackberries, put over a low heat and stir until the sugar has dissolved. Bring to the boil and simmer for 5 minutes. Remove from the heat and leave to infuse for 20 minutes.
Return the pan to the heat, adding the pears and blackberries. Bring to a simmer and submerge the pears for 45 minutes. Turn them every 10 minutes. They should be ruby red and just cooked. Remove from the pan and set aside to cool.
Sieve the poaching liquid. Bring back to the boil, reduce until thick and syrupy, then cool.
Place your meringue on a plate. Whip the double cream until soft peaks form and layer over the meringue. Stand the pears on top of the cream in a circle, pour the syrup over and let it drizzle down the sides of the meringue. Finally, sprinkle the pistachios over the top. Serve immediately.