Peel two potatoes and slice them into fries.
Boil them in salty water with a splash of vinegar for about 3 minutes, then drain and pat them completely dry.
Toss in cornstarch, freeze for 2 hours, and deep-fry at a low temp (around 150 °C / 300 °F) for 3 minutes.
Let them rest for 15 minutes, crank the oil up to high heat (around 190 °C / 375 °F), and fry again for 5–10 minutes until perfectly crispy and golden.
