1. Pre-heat the oven to 170°C/150°C fan forced.
2. To make the chocolate pastry, sift the flour, cocoa powder and salt into a bowl, add the butter and rub together using your fingertips until the mixture resembles fine breadcrumbs. Stir in the sugar.
3. Add the egg yolk and 3-4 teaspoons of chilled water to bring the mixture together to form a dough. Wrap in plastic food wrap and place into the refrigerator or a cool place to rest for approximately 20 minutes.
4. Roll out the pastry on a floured work surface to form a rectangle 18cm x 38cm and carefully line the tin. For easy transfer to the tin, use a large thin-bladed metal turner or palette knife to loosen the pastry from the worktop, roll the pastry around the rolling pin then unroll into the tin starting from one end and finishing at the other.
5. Carefully press the pastry into the flutes, trim any excess above the tin and prick the base with a fork in several places. Place a piece of scrunched up baking paper inside, large enough to cover the base, and fill with baking beans. Bake blind for 15 minutes, remove the paper and baking beans and return to the oven to bake for 20 minutes. Leave to cool in the tin.
6. To make the cherry filling, place the cherries, lemon zest, water and cherry jam into a small pan, bring to the boil and cook for 8-10 minutes until the fruit has softened. Stir in the cornflour and water mixture and continue to cook until thick and glossy. Stir in the kirsch or brandy and set to one side to cool.
7. To make the ganache filling, place the chocolate into a bowl and heat the double cream in a small pan to boiling point. Pour the hot cream over the chocolate and leave to melt. Once melted stir to combine and allow the mixture to completely cool and become thick. Sieve in the icing sugar and using an electric whisk whip the mixture for 2-3 minutes until it has become lighter in colour and texture.
8. To make up, spread the cherry filling over the base of the baked pastry case reserving a few spoons for decorating. Top with the ganache filling, smooth over the surface and place into the refrigerator for approximately 30 minutes to set.
9. Remove the filled tart from the tin and slide from the base onto a serving plate.
10. Decorate with piped swirls of whipped cream, grated chocolate and the reserved cherry filling. Finish with some fresh mint leaves.

Cook's notes:

• The pastry can be made a few days in advance but will require to be left at room temperature to soften before rolling.
• To save time, make the fillings whilst the pastry is resting and baking.
• When chilling the dessert for longer periods remove from the fridge 30 minutes before serving.