Shortcrust pastry dough
Mix the flour, sugar and salt in a bowl. Add the margarine and rub together by hand to form an even, crumbly mixture. Pour in the water and mix quickly to form a soft dough; do not knead. Flatten the dough, cover and chill for approx. 30 mins.
Roll out the dough on a lightly floured surface, place in the prepared tin, prick firmly, chill for approx. 15 mins. Cover the dough with baking paper, weigh down with dried pulses.
To blind bake
Approx. 15 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, remove the baking paper and pulses, bake for a further 10 mins. Remove from the oven, leave to cool completely on a rack.
Puree the mango, transfer to a pan and add the sugar, place on the heat and stir until the sugar dissolves. Combine the water, lemon juice and agar-agar in a separate container, pour into the puree, bring to the boil while stirring, boil for approx. 2 mins., allow to cool slightly. Pour the jelly through a sieve and onto the tart base, leave to cool. Cover and chill for approx. 4 hrs.
Place the chocolate in a bowl, heat the coconut milk in a small pan, pour on top of the chocolate, leave to stand for approx. 1 min., stir until smooth, allow to cool slightly. Pour the ganache on top of the jelly layer, leave to cool. Cover and chill for approx. 1 hr.
Arrange the mango slices on top of the tart in a rosette shape, sprinkle with the pistachios.