Leaving the skin on, cut the potatoes into long thin strips and put in a large bowl of clean water to remove some starch, prevent them from sticking together, and stop the oxidizing process.
In a cast iron skillet fitted with a thermometer, or a small fryer, heat the oil until it reaches 275 to 300 degrees F. Remove the potatoes from the water and pat dry. Working in small batches, fry the potatoes until they go from shiny to matte, 3 to 5 minutes (this is also called blanching). Drain well on paper towels. Re-heat the oil until it reaches 350 degrees F and fry the potatoes again, also in small batches, until they are golden brown and crispy on the outside but soft and chewy on the inside.
Remove from the oil, drain well, and toss with sea salt and malt vinegar, or any other seasoning you prefer. You can also fry fresh herbs such as rosemary, sage, and thyme with the potatoes. Serve hot.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.