Preheat the oven to 200C/180C Fan/Gas 6. Line a 23x33cm/9x13in Swiss roll tin with greased non-stick baking paper.
Whisk the egg whites in a clean large bowl using an electric mixer on full speed until very stiff. Gradually add the sugar, a teaspoon at a time, and still on high speed, whisking well between each addition. Whisk until very, very stiff and glossy and all the sugar has been added.
Then add in the cider vinegar
Spread the meringue mixture into the prepared tin.
Bake the roulade for 20 minutes until golden brown and firm to the touch.
Remove and turn upside down on a piece of non-stick baking paper. Carefully peel the paper from the base of the meringue and leave it to cool for about 10 minutes.
Fill with Chantilly cream and fresh Irish berries.
