Dry-fry the hazelnuts in a pan over medium heat for 5 minutes until golden-brown.
Cool the toasted hazelnuts and chop them roughly.
Draw two 25cm circles and one 20cm circle onto separate pieces of baking parchment.
Grease three baking trays and line them with the parchment paper circles-side down.
Preheat the oven to 150°C.
Whisk egg whites in a large bowl until stiff peaks form.
Add caster sugar gradually, one tablespoon at a time, whisking constantly.
Whisk in the vanilla extract and cornflour until the mixture is glossy.
Fold in most of the chopped hazelnuts, reserving a few for the garnish.
Spread the meringue mixture into the circles on the prepared trays.
Reduce the oven temperature to 130°C.
Bake the meringues for 90 minutes until firm and set.
Cool the meringues completely and then peel off the parchment paper.
Melt the chocolate in a heatproof bowl over simmering water and let it cool slightly.
Whip the double cream and icing sugar together until soft peaks form.
Fold the crème fraîche into the whipped cream until combined.
Layer a large meringue with cream filling, drizzled chocolate, and raspberries.
Repeat with the second large meringue and top with the final small meringue.
Finish with remaining filling, chocolate, raspberries, reserved hazelnuts, and a dusting of icing sugar.