1. Prep the potatoes and place them in a large bowl filled with ice water. Soak for 1 hour, discard water, and soak again until ready to fry. This helps to remove the starch and therefore reduces the chances that your fries will stick together. You can soak them for longer than 1 hour if you want to prepare them ahead of time.
2. Heat oil in a large saucepan or stock pot. If you have a thermometer, heat to 325F. The oil shouldn’t be boiling or even bubbling.
3. Dry potato pieces on paper towels. Test the oil temperature with one fry -- it should boil up but not turn brown, even if it sits in the oil for a few minutes. Fry in batches. You want the fries to have room to swim, and you also don’t want to reduce the oil temperature too quickly by overwhelming the pot with cold potatoes. Stir them a little to make sure they don’t stick (although soaking them should prevent this). Be gentle -- the more they cook, the softer they get, and the easier they are to break!
4. Fry for 4-6 minutes until the fries are opaque and softened, but not brown. Drain batches on paper towels. When all the fries have been through the first cooking, turn up the heat to just over the medium mark (375F if using a thermometer). The oil will bubble a little. Again, test with a single fry. It should brown up now.
5. Working in batches, cook the fries until they are golden brown, about 3-5 minutes. They are sort of delicate between the first and second fry, so be gentle when moving them. In my experience, the fries looked a little crispier than they actually were, so give them a little more time than you feel like they need if you like crispy fries.
6. Remove them from the oil with a slotted spoon and drain on a paper towel. Salt them immediately, before the oil dries, or else the salt won’t stick.