For chocolate pastry: Blitz butter, flour, cocoa and icing sugar in a food processor until the mixture resembles fine breadcrumbs. Add the egg yolk and water mix whilst the mixer is running and blitz to combine. When combined, turn onto a lightly floured work surface and knead lightly until smooth. Wrap with cling film and refrigerate until firm (1-2 hours). Roll pastry on a lightly floured work surface, then use to line the base of a 22cm round tin. Rest for 1 hour in the freezer. Preheat oven to 200 C/ 180 C fan and blind bake the pastry for 15-20 minutes, until almost dry then remove the baking paper and beans and bake until cooked through - about another 5 - 7 minutes. Set aside to cool whilst you make the filling.
For the filling: Reduce oven to 110C. Whisk yolks in a heatproof bowl. Combine cream, sugar and red wine in a saucepan over medium heat and bring to the boil. Remove from heat, add the chocolate and stir until smooth. Pour the cream mixture over the yolks and whisk to combine, then strain through a fine sieve into the pastry case. Bake the tart until almost set (30-35 minutes). Remove from the oven and allow to cool completely, then place into the fridge for 2 hours. When ready to serve, sprinkle with caster sugar and caramelise with a blowtorch.