Preheat the oven to 150℃ /130℃ fan/gas mark 2. Draw a large circle on a sheet of non stick baking parchment using a dinner plate as a guide. Turn the paper upside down (make sure the circle is dark enough to show through the parchment) and place on a baking sheet.
Whisk the egg whites until standing in stiff peaks, then gradually whisk in the caster sugar a spoonful at a time until all the sugar has been added and you have a stiff glossy meringue.
Sprinkle the vinegar and cornflour on top and whisk in.
Spoon the mixture onto the centre of the parchment and spread out using the drawn circle as a guide. Make a dip in the centre and swirl the meringue in a mound around the edge of the circle.
Bake in the centre of the oven for 1 hour. Turn off the oven and allow to cool completely in the oven without opening the door.
To make the coulis
Push the raspberries and redcurrant if using through a sieve into a bowl and discard the seeds. Stir in the caster sugar and set aside.
Hull the fruit if required. Cut larger strawberries into quarters or halves. Set aside some fruit to decorate. Toss the remaining fruit in a little coulis.
Spoon the coated berries into the centre of the pavlova. Whip the cream until standing in soft peaks and spread over the berries.
Arrange the remaining fruit on top. Serve the remaining coulis, drizzled over the top of the pavlova or separately.
The meringue will keep in an airtight container unfilled for several days. Assemble just before serving.Not suitable for freezing.Nutrition information is approximate and is meant as a guideline only.