Line 3 baking sheets with nonstick baking paper.
Whisk the egg whites in a large clean bowl until they form stiff peaks. Add the sugar a spoonful at a time and continue to whisk until thick and glossy. Fold in the vinegar with a large metal spoon.
Fold half the hazelnuts into the mixture, then divide it between the prepared sheets, spooning the meringue into 3 rounds roughly 18 cm (7 inches) in diameter.
Place in a preheated oven, 150°C (300°F), Gas Mark 2, for 45 minutes, then switch off the oven and leave the meringue to cool.
Whip the cream in a bowl until it forms soft peaks, spoon the cream over 2 of the meringues and top each with the raspberries and remaining nuts, reserving a few raspberries for decoration.
Stack the meringues with the plain one on top, then dust with a little cocoa powder and decorate with the remaining raspberries. Serve on the same day or chill for up to 2 days.