- 4 large potatoes, preferably Maris Piper
- sunflower oil, for deep frying
- flaked sea salt
- malt vinegar
- Peel the potatoes and cut lengthways into roughly 1cm/½in slices. Cut each slice into fairly thick chips and rinse in a colander under plenty of cold water to remove excess starch. (If you have time, it's worth letting the chips soak in a bowl of cold water for several hours, or overnight.) Pat dry with kitchen paper.
- Heat a deep, heavy-bottomed saucepan half-full of the sunflower oil to 130C. It's important to use a cooking thermometer and check the temperature regularly. Alternatively, use an electric deep-fat fryer heated to 130C. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
- Using a large, metal, slotted spoon, gently lower half the chips into the hot oil and stir carefully. Fry for ten minutes, or until cooked through but not browned.
- Remove the chips from the pan with a slotted spoon and set aside to drain on plenty of kitchen paper. Repeat the process with the remaining chips. (The chips can be left for several hours at this stage.)
- When ready to serve, reheat the oil to 190C. With a slotted spoon, lower all the par-cooked chips gently into the pan and cook for 4-5 minutes, or until crisp and golden-brown. Remove from the pan with a slotted spoon and drain on kitchen paper.
- Tip into a serving dish and sprinkle with salt and vinegar to serve.