120 gmdark chocolate (56%-60% cocoa solids), finely chopped, plus extra shaved to serve250 gmeggwhites (from about 8 eggs)250 gmcaster sugar250 gmpure icing sugar50 gmDutch-process cocoa3 tspcornflourChocolate sauce65 gmdark chocolate (58% cocoa solids), coarsely chopped10 gmunsalted butter75 gm (1/3 cup)caster sugar70 gmliquid glucose2 tspDutch-process cocoa powder, sieved100 mlpouring creamCrushed raspberry cream400 mlthickened cream400 gmcrème fraîche50 gmpure icing sugar, sievedScraped seeds of 1 vanilla bean120 gmraspberries, plus extra to serve3 tspbalsamic vinegar
Preheat oven to 120C. Trace a 25cm x 12cm rectangle on each of 3 sheets of baking paper, then place each sheet pencil-side down on a lightly greased baking tray. Melt chocolate in a bowl over a saucepan of simmering water, stirring occasionally until smooth. Set aside.
Whisk eggwhite, caster sugar and a pinch of salt in an electric mixer until firm, glossy peaks form (6-7 minutes). Sieve icing sugar, cocoa and cornflour onto mixture and fold to combine. Fold in melted chocolate to create a ripple effect, then divide evenly among prepared trays, spreading within the rectangle templates. Bake, swapping and turning trays occasionally, until crisp and dry (1-1¼ hours). Turn off oven and leave meringue in to cool completely, then store in airtight containers for up to 2 days until required.
Meanwhile, for chocolate sauce, melt chocolate and butter in a heatproof bowl placed over a saucepan of simmering water, stirring occasionally until smooth (2-3 minutes). Combine remaining ingredients and 100ml water in a saucepan and bring to the boil, stir in chocolate mixture. Bring back to the boil, season with a good pinch of sea salt flakes and refrigerate to chill. Chocolate sauce can be made up to a week ahead.
For crushed raspberry cream, whisk cream, crème fraîche, icing sugar and vanilla seeds in a bowl to soft peaks. Crush raspberries with balsamic vinegar in a separate bowl and fold into cream mixture to form a ripple effect.
To serve, place a meringue rectangle on a serving platter, spread with a third of the crushed raspberry cream, top with a third of the raspberries, then with another meringue rectangle. Repeat layering, finishing with raspberries, then drizzle with chocolate sauce, scatter with shaved chocolate and serve.