First make the pastry. Sift the flour and salt into a mixing bowl. Using your fingertips, rub the butter into the flour, lifting the mixture up and dropping it back into the bowl—you want to keep the mixture light and airy. When it resembles fine breadcrumbs, mix in 2–3 tablespoons of cold water. Bring the pastry together, adding a little more water if needed, then knead lightly on a floured work surface to create a smooth, solid ball. Wrap in plastic wrap and chill for 20 minutes.