Start by making the pastry, which doesn’t take long at all… Put the flour, butter, cold water and a pinch of salt in a large mixing bowl. Using your fingertips and working quickly, rub the cubed butter into the flour until it becomes the texture of coarse breadcrumbs. Now bring the dough together into a smooth ball with your hands, kneading a little and adding a dash more cold water if needed. Lightly flour a work surface and use a rolling pin to roll the pastry out into a circle, roughly the same size as your pan and about 2.5 cm/1⁄2 inch thick. Carefully transfer the pastry to a plate, cover with a kitchen towel and leave in the fridge while you make the filling.