Peel the potatoes and cut into 1.5cm-thick lengths. Place in a medium saucepan filled with cold water and bring to the boil. Cook until tender when a sharp knife is inserted. Remove from the heat, drain well and pat dry. Place in a single layer on a tray lined with paper towels and refrigerate until cold.

Heat the oil in a deep fryer to 140C. Cook chips in batches for 3-4 minutes, until sealed and slightly coloured. Remove and place on wire rack to drain. Increase the heat to 180C and return chips to the hot oil. Cook for a further 5-6 minutes, until crisp and golden.

Remove and drain on fresh paper towels. Season with sea salt and serve immediately.

Look out for russet burbanks. The sugar content makes them caramelise and brown when frying, for a superior chip.