Preheat the oven to 180°C (160° Fan, Gas Mark 4). To make the pastry, sift the flour and Cocoa together and place in a food processor with the sugar. Pulse to combine and then add the butter. Blitz until the mixture resembles fine breadcrumbs and then add the egg yolks and water. Blitz again until the mixture comes together. Gently knead the pastry into a flat disc and wrap in cling film. Chill for half an hour.

When the pastry has chilled, lightly dust your work surface with icing sugar, roll out the pastry and line your tart tin. Line with a sheet of greaseproof paper and fill with baking beans. Bake blind for around 12-15 minutes or until the pastry has set. Remove the baking beans and paper and return to the oven for a further 5 minutes. Leave to cool.

For the caramel, put the sugar in a heavy-based saucepan over a medium heat and leave to melt. As the sugar starts to liquify around the edges, swirl the pan so the dry sugar is incorporated into the molten sugar. Continue like this until all of the sugar has fully melted and then simmer until you achieve a rich caramel colour.

Take off the heat and add the butter and cream, taking care as the caramel will bubble up. Stir well until all the ingredients have been incorporated and add the salt to taste.

For the chocolate filling, break the Chocolate into a bowl with the butter. Put the cream and sugar in a saucepan and heat to boiling point. Pour over the Chocolate and butter, stirring well until all the Chocolate has melted and you have a nice glossy ganache.

To make the tart, pour the salted caramel into the base of the tart case, spreading to create an even layer. Carefully pour the chocolate ganache over the caramel and smooth flat. Chill in the fridge for a couple of hours to set. Leave to come to room temperature before serving.