Preheat the oven to 200°C (180°C Fan, Gas Mark 6). For the pastry, sift the flour and Cocoa into a bowl. Stir in the sugar and rub in the butter to form a mixture that resembles fresh breadcrumbs. Mix in the egg yolk and bring the mixture together with your hands to form a firm pastry dough.

Knead gently on a lightly floured surface then roll out thinly. Cut out 8 x 10cm (4inch) circles, re-rolling as necessary and use to line 8 x 8cm (3 ¼ inch) loose-bottomed fluted tart tins. Trim the edges and chill for 30 minutes.

Line each tart with a small piece of baking parchment and fill with baking beans or raw rice. Bake for 10 minutes then carefully remove the parchment and beans or rice, prick the bases with a fork and return to the oven for a further 7-8 minutes until the pastry is cooked through. Leave to cool in the tins before removing and placing on a wire rack.

For the filling, put the sugar and syrup in a saucepan with 60ml (4 tbsp) water. Gently swirl the pan  over a low heat, rather than stirring, until melted. Bring to the boil and cook for 4-5 minutes until richly golden and caramelised.

Immediately remove from the heat and stir in the butter and cream, taking care as the mixture will hiss and bubble, then pour into the pastry cases. Leave to cool completely.

For the ganache, break the Extra Dark Chocolate into pieces and put in a small saucepan with the butter and 15ml (1tbsp) water. Heat gently, stirring occasionally, until melted together – do not boil.

Carefully spoon a thin layer of the ganache over each tart, tapping gently on the work surface to smooth the surface. Chill for at least 1 hour to set.

To serve, stand at room temperature for 20 minutes then sprinkle each with a tiny pinch of salt flakes.