Pair sweet meringue with tart blackberrys for a wonderful dessert.
For the meringue base, preheat the oven to 140C/275F/Gas 1. Line a baking tray with baking parchment.
Whisk the egg whites in a clean glass or metal bowl until soft peaks form when the whisk is removed. Add the sugar, a spoonful at a time, and continue to whisk until firm peaks form when the whisk is removed and the mixture is glossy. Whisk in the cornflour and vinegar.
Place tablespoonfuls of the mixture onto the lined baking tray and bake in the oven for 10 minutes. Turn the oven off and leave the meringues in the oven with the door closed for 2-3 hours, or preferably overnight, until crisp but uncoloured.
Meanwhile, for the blackberry parfait, blend the blackberries, custard and lemon juice to a purée in a food processor. Gently fold the purée into the whipped cream until well combined.
In a separate bowl, whisk the egg whites until soft peaks form when the whisk is removed, then gradually add in the caster sugar, whisking continuously until glossy, stiff peaks form. Fold half of the egg whites into the blackberry mixture until well combined, then carefully fold in the remaining egg whites until just combined.
Spoon the parfait into a 25cm/10in diameter x 5cm/2in high springform cake tin lined with cling film and tap the side lightly with a spoon to release any large air pockets.
Freeze the parfait for at least 4 hours, but preferably overnight, until solid.
For the Italian meringue topping, heat the sugar and water in a saucepan until the mixture reaches 110C/230F on a sugar thermometer. (CAUTION: Boiling sugar syrup can be dangerous. Do not leave unattended.)
Meanwhile, using an electric whisk, whisk the egg whites and lemon juice in a clean glass or metal bowl until firm peaks form when the whisk is removed.
As soon as the sugar syrup reaches 121C/250F, remove the pan from the heat.
Immediately resume whisking the egg whites. With the whisk set to its lowest speed, pour in the sugar syrup in a steady stream. (CAUTION: Keep the syrup clear of the beaters as hot syrup could splash back onto your hands.) Continue whisking for 4-5 minutes, until the mixture is slightly cooled. Spoon the meringue into a piping bag fitted with a teardrop-shaped nozzle.
For the blackberries, fry the butter and blackberries in a non-reactive frying pan over a high heat for 1-2 minutes, or until just softened. Add the blackberry liqueur. Carefully set the liqueur alight with a kitchen match. Allow the flames to flare up and die down, then continue to cook for a further minute.
To serve, crumble some of the crisp meringue base into the centre of each of eight plates. Using a hot knife, cut eight slices of blackberry parfait and place one on top of each serving of meringue. Pipe some Italian meringue onto the top of the parfait. Using a cooks' blow torch, brown the tops of the meringue. Spoon some warm blackberries alongside and serve immediately.
