1. Pre-heat the oven to 140°C, gas mark 1.
2. Line a large baking tray with non-stick baking paper.
3. Whisk the egg whites in a food processor, or large bowl, until the mixture forms stiff peaks.
4. Gradually add the sugar - one spoon at a time. Continue to whisk until all of the sugar is combined. If using a food processor, I’d suggest the top speed. By hand, I’d suggest recruiting a helper to take turns with! The finished mix will form stiff peaks, and be very shiny.
5. Pile the meringue onto the centre of the lined baking tray,/p>spread to approx. 20cm. Wet a spatula under a tap (this will stop the mix sticking to it) and gently create a dip in the centre of the mixture.
6. Cook in the oven for approx. 1hr 20mins. Reduce the heat a little if the meringue begins to brown too much. Turn the oven off and allow the meringue to cool in the oven. Once cooked, the meringue can be kept in a dry cool place for up to 3 days before serving.
7. Place the cider and Crème de Cassis into a small saucepan, bring to the boil and simmer until it has reduced by about a 1/4 and resembles a syrup. Gently stir in the blackberries. Leave to cool.
8. Whisk the cream until it begins to form soft peaks.
9. Split and seed the vanilla pod, add to the cream.
10. Spoon the cream into the centre of the pavlova. Then add the blackberry mix. Tear the mint leaves into small pieces and sprinkle over to decorate.