Peel the potatoes and then cut them into 1cm (½") thick chips. Don't worry about the roundness, keep aiming for a 1cm profile (just under ½"), the smaller chips go crispy, which are my favourite.
Soak the potatoes in cold water for 15 minutes, changing the water once during this time. Then remove the chips and dry them thoroughly.
Preheat the oil in a deep fat fryer to 140°C or 285°F. Add your chips to the oil, and cook your chips until they are soft to the tip of the knife, which will take around 4-5 minutes.
Remove the basket from the oil and turn the heat up to 190°C or 375°F and as soon as the oil has come to temperature drip the chips back into the fryer and cook for 2 minutes.