WHAT YOU NEED

1. To make the sweet shortcrust pastry, place the butter in the bowl of an electric mixer fitted with a paddle attachment. Add the icing sugar and mix until creamy, then add the flour and a pinch of salt. Mix for 30 seconds, then add the egg and continue to mix for 10 seconds or until the dough comes together to form a ball. Flatten the dough gently intno a disc with your fingers. Wrap in plastic film and rest in the fridge for 20 minutes. Tear off two 40cm sheets of baking paper;

2. Remove the dough from the bowl and rollout between the baking paper until 3mmthick, then line a tart tin with a removablebase (mine is 28cm long) with the pastry.Peel off one sheet of the baking paper,then invert the pastry over the tin, gentlylaying it in the tin. Remove the secondsheet of baking paper and mould thepastry up the sides of the tin with yourfingertips. Remove any excess pastry withyour thumb by pressing down along theedges of the tin. Refrigerate for 30 minutes;

3. Preheat the oven to 180°c fan-forced (200°c conventional);

4. To make the pistachio crumble, bring the water to the boil in a small saucepan over high heat. Sprinkle the pistachios into the pan and simmer for one minute then remove from the heat. Drain the pistachios and place on a clean tea towel. Using the tea towel, gently run off the skins. Pat the peeled pistachios dry, then pulse in a food processor to form a coarse meal. Transfer to a bowl, then add the butter, sugar and flour and rub together with your fingertips to combine roughly. Set aside;

5. Line a small baking tray with baking paper and sprinkle the crumble mixture onto the tray, then bake for 10 minutes or until golden. Set aside to cool;

6. Press a sheet of baking paper onto the pastry, then fill with baking beads, dried beans or rice and bake for 12 minutes. Remove the weights and baking paper and bake the pastry for another 5 minutes or until it is golden and dry. Set aside;

7. Using an electric mixer, cream the butter and sugar together until creamy, then, with the motor running, add the eggs and egg yolk, one at a time, continuing to mix after adding each one. Add the almond essence, lemon zest, ground almonds, flour and pistachio paste (if using) and mix to incorporate;

8. Pipe or spoon the almond mixture into the tart shell to reach the top of the tart tin, then level the surface with the back of a spoon. Gently press the plum halves into the almond mixture, placing them at even intervals along the tart. Baking the tart for 30 minutes or until golden;

9. Remove the tart from the oven and leave to cool. Sprinkle the crumble generously over the tart and serve.