Place the butter in a bowl, mix in the salt and sugar using the whisk attachment on a hand mixer. Combine the flour and cocoa, add along with the water, mix quickly to create a soft dough – do not knead. Flatten the dough, cover and chill for approx. 30 mins. On a lightly floured surface, roll the dough into a circle approx. 2 mm thick, place in the prepared tin, prick the base firmly with a fork, chill for approx. 15 mins. Cover the dough with baking paper, weigh down with dried pulses.
To blind bake
Approx. 10 mins. in the lower half of an oven preheated to 180°C. Remove the baking paper and pulses, bake the tart base for a further 15 mins. Remove from the oven, allow to cool slightly, then remove from the tin and leave to cool completely.
Heat the cream in a pan, remove the pan from the heat. Add the chocolate, melt and stir until smooth. Allow the ganache to cool slightly. Spread the jam over the base, smooth down. Spread the ganache on top, smooth down, cover and chill for approx. 2 hrs. Top with cherries.