Chunky Orange Marmalade Tart

• 100 g (4 oz) self-raising flour
• A pinch of salt<

For the pastry, sift the flour and salt into a bowl and mix in the mashed potato. Rub in the butter with your fingertips until the mixture resembles crumbs, then bring together into a dough, adding a little cold water to bind if necessary. Wrap in clingfilm and chill for 1 hour.

Preheat the oven to 200°C/400°