Preheat the oven to 160 °C. Grease a 30 x 18 cm tart tin with nonstick spray.
1. Pastry Put all the ingredients except the water in the bowl of a food processor and pulse until the mixture resembles breadcrumbs. Add the water and process on high until the dough comes together.
2. Turn out the dough and press together lightly. Cover with clingfilm and rest for at least 15 minutes.