Preheat the oven at 150°C and grease and line a Swiss roll tin with baking paper. Whisk the egg whites till stiff in an electric mixer fitted with a whisk. Whilst still mixing, gradually add in the caster sugar and continue beating until the mixture is smooth, stiff and shiny. Carefully fold in the corn flour, vinegar and vanilla. Pour the meringue into the prepared tin and spread evenly. Bake for 15 minutes. Remove from oven and allow to cool down completely. When cold, flip over upside down on a sheet of baking parchment and carefully remove the baking paper. Whip the double cream into stiff peaks with the 100g icing sugar and vanilla. Spread ¾ of the cream evenly over the meringue and top with most of the berries. Roll the meringue with the aid of the baking sheet to form a Swiss roll. Decorate the top with the reserved cream and berries, sprinkle with the toasted almonds and dredge with extra icing sugar.