Pre-heat your oven to gas mark 6 - with a baking tray on the centre shelf. Grease your pie dish with butterand line with the pastry - press it carefully into shape and trim any overhanging edges. Prick the base all over with a fork. Refrigerate for 30 minutes. Cover the edges with kitchen foil and place the pie dish on the baking tray. Bake for 15-20 minutes until the base is firm.