Preheat the oven to 190C/Gas5
Whisk the egg whites to firm peaks, then add the caster sugar and the coffee, whisking well between each addition
Once all of the caster sugar and coffee is incorporated into the egg whites, fold in the icing sugar; spread the meringue evenly into a lined tray 25.5cm x 35cm, dust with icing sugar and bake for 15-20 minutes; check if it is cooked by inserting a skewer into the centre, which should come out clean
Remove the meringue from the oven, and let it cool; turn the oven up to 200C/Gas6; put the hazelnuts in a bowl, add the caster sugar and toss together; spread the nuts over a small baking sheet in an even layer and bake for 4-5 minutes or until golden and lightly caramelised; remove from the oven and allow to cool completely
Whip the double cream and mascarpone together until thick; transfer a third of the mixture to a separate bowl; add the cooled hazelnut and sugar mixture to the remaining two thirds, stir in well and set aside
Melt the chocolate and allow to cool slightly; stir it into the third of the mascarpone and cream mixture; make sure you do this briskly because the chocolate will begin to set on contact with the cold cream mixture
Once the meringue is cool, lay it crisp-side down, on to a large sheet of baking parchment, then gently peel off the lining parchment; spread the hazelnut cream over the top, leaving a 3cm border around the edges of the meringue; smooth the chocolate cream over the top, leaving a 2cm border around the edges of the hazelnut cream
With the long side of the meringue towards you roll the edge of the meringue over so that it meets the chocolate mousse and continue rolling using the parchment to help you, until you have a long log
Make sure that the seam is facing downwards, then roll up the roulade in the baking parchment and place in the fridge to chill; remove the roulade from the fridge at least 20 minutes before serving, dust with icing sugar and cut into slices
Servings 0