Wash the potatoes well and cut them into sticks with the skin on. 

Give the potatoes a short boil in water with 1 tbsp. vinegar.

Drain the water without damaging the potatoes.

Repeat the process 2 more times, and dry them well with a dish towel/paper towels.

Chill them, preferably in the freezer if you have the option.

Deep fry the potatoes just before serving in 180 degrees Celsius (356 degrees Fahrenheit) hot oil. They should turn golden, which can take 8-12 minutes.

If you are not using a deep fryer, you can check the oil temperature by sticking the end of a potato into the oil - if it bubbles around the potato, the oil is typically hot enough. 

Sprinkle with salt before serving.