Put the cut chips into a bowl under running water for 5 minutes to wash the starch off. Place 2 litres of cold tap water in a large saucepan and add the potatoes. Place the pan over a medium heat and simmer until the chips are almost falling apart (approximately 20–30 minutes, depending on the potato). Carefully remove the cooked chips and place them on a cooling rack to dry out. Then place the rack in the freezer for at least 1 hour to remove more moisture. Heat a deep-fat fryer or a deep pan no more than half filled with oil (to a depth of around 10cm) to 130ºC. Fry the chips in small batches until a light crust forms (approximately 5 minutes), remove from the oil and drain on kitchen paper. Put the potatoes on a cooling rack and place in the freezer for at least 1 hour. (At this stage, if you don’t want to cook and serve immediately, the chips can be kept in the fridge for 3 days.) Heat the oil in the deep-fat fryer or deep pan to 180ºC and fry the chips until golden (approximately 7 minutes). Drain and sprinkle with salt.