Be sure to blind-bake the pastry until light golden so it will
be crisp once the filling is cooked. Cool the tart completely
before you serve it, and if it's a hot day place it in the fridge
to help set the filling.
180 gmdark chocolate (55 per cent - 60 per cent cocoa solids)85 gmbutter, diced4eggs, separated50 gmcaster sugar80 ml (1/3 cup)pouring cream, whisked to soft peaks200 gmblackberries, plus extra to serveShortcrust pastry250 gm (1 cup)plain flourScraped seeds of 1 vanilla bean150 gmchilled butter, diced1egg
For shortcrust pastry, process flour, vanilla seeds and a pinch of salt in a food processor to combine, add butter and process until just combined with flecks of butter still showing.
Add egg and 2 tsp cold water and pulse until combined, then turn pastry out onto a bench, knead with the palm of your hand to just bring dough together without overworking it, then wrap in plastic wrap and refrigerate for 1 hour to rest.
Roll pastry between 2 sheets of Go-Between (plastic sheeting) or baking paper to a 35cm round. Remove top sheet and invert pastry into a 24cm loose-bottomed tart tin. Press pastry gently into the edges, then remove remaining sheet, trim edges and refrigerate for 30 minutes to rest.
Preheat oven to 175C. Blind-bake tart case until starting to turn golden (35 minutes; see cook’s notes p184). Remove paper and weights, reduce oven to 160C and bake, gently pressing pastry down with a clean tea towel if it puffs up and rotating tin so pastry cooks evenly, until golden and base is set (10-15 minutes).
Meanwhile, in a heatproof bowl placed over a saucepan of simmering water, melt chocolate and butter (5-7 minutes), stirring occasionally, until smooth. Cool for 5 minutes. Whisk eggwhites in an electric mixer until frothy, then gradually add sugar, whisking until soft peaks form. Whisk yolks into chocolate mixture, fold in eggwhite in batches, then fold in cream to just combine.
Scatter blackberries in pastry case, then pour chocolate mixture over blackberries, spreading evenly. Bake until a skewer inserted withdraws clean (20-25 minutes). Cool tart in tin on a wire rack (30-40 minutes), then remove tart ring and cool to room temperature (1-1½ hours). Serve with extra blackberries. This tart is best served on the day it’s made.