When you wish to roll the pastry tart, lightly butter the form. Remove the pastry from the fridge, shape into a four-centimetre roll and slice into one-centimetre thick disks. Place the disks in a fish-scale pattern in the base of the tart form. Using your fingers, push the pastry down to create a smooth surface and up the sides to fill the tart shell. Alternatively, you could roll the pastry out to a three-millimetre-thick sheet and line the tart form with this.