To make the pastry, process flour, cocoa, icing sugar and butter in a food processor until the mixture resembles fine breadcrumbs. Add the egg yolk and water and pulse until just combined. Press the dough together into a ball, flatten into a disk, cover with cling wrap and refrigerate for 15 minutes

Divide dough into 10-12 even portions. Roll out each portion until 3mm thick. Line a 2cm deep 7cm fluted flan tin, with removable base, with the pastry and trim excess. Repeat with remaining pastry, re-rolling any excess pastry, if necessary. Place tins on a baking tray and chill in freezer for 30 minutes

Cover each pastry shell with baking paper and fill with pastry weights. Bake at 200°C for 10 minutes. Remove weights and paper and bake for a further 5 minutes or until cooked through and try to the touch. Cool completely

Combine all ingredients in a saucepan over medium-low heat. Cook, stirring for 8-10 minutes or until golden. Spoon caramel evenly over each pastry case. Cool

To make the chocolate ganache, place chocolate and cream in a heat-proof bowl over a saucepan of simmering water. Stir until melted.

Pour over the caramel. Refrigerate to set

Remove tarts from fridge 30 minutes before serving, and sprinkle with extra sea salt