Cut potatoes into French fry shapes, about 3/8-inch wide and thick, using a mandoline or a knife. Soak potatoes in a large bowl of cold water for about 30 minutes. Drain and pat potatoes dry with a clean towel.

Heat oil in a deep-fryer or deep saucepan to 275°F (135°C).

Gently lower 1/4 of the potatoes into the hot oil and cook, stirring occasionally, for 2 minutes. Transfer cooked potatoes to a clean towel using a slotted spoon. Repeat frying with remaining potatoes.

Heat the same oil to 350°F (175°C). Fry potatoes again, working in batches, until golden brown, about 5 minutes. Transfer fries to a clean kitchen towel using a slotted spoon.