2) With the motor running, add the ice water all at once through the feed tube. Keep hitting the pulse button to combine, but stop the machine just before the dough comes together. Turn the dough out onto a well-floured board, roll it into a ball, cut in half, and form into 2 flat disks.
3) Wrap each of the disks in cling film and refrigerate for at least 1 hour. If you only need 1 disk of dough the other disk of dough can be frozen.
4) Preheat the oven to 230C/Gas Mark 8. Meanwhile, line a baking sheet with parchment paper. Roll the shortcrust into a 28cm circle on a lightly floured surface. Transfer it to the baking sheet.
For the filling:
1) Cut the peaches and plums in wedges and place them in a bowl with the blueberries. Toss them with 10g of the flour, 15g of the sugar, the orange zest, and the orange juice. Place the mixed fruit on the dough circle, leaving a 4cm border.
2) Combine the remaining flour and sugar and the salt in the bowl of a food processor fitted with a steel blade. Add the butter and pulse until the mixture is crumbly. Pour into a bowl and rub it with your fingers until it starts to hold together. Sprinkle evenly over the fruit. Gently fold the border of the shortcrust over the fruit, pleating it to make an edge.
3) Bake the crostata for 20 to 25 mins, until the crust is golden and the fruit is tender. Let the crostata cool for 5 mins, and then use 2 large spatulas to transfer it to a wire rack. Serve warm or at room temperature.