Peel the potatoes, then cut them into thick slices. Slice each piece into strips to make French fries.
Place the potato strips in a large bowl. Add salt, distilled white vinegar, and enough water to cover the potatoes.
Mix well with your hands, then let the potatoes soak for 10 minutes. Salt and vinegar help keep the potatoes from turning brown.
After soaking, rinse the potatoes under cold running water to remove excess starch.
Bring a pot of water to a boil. Add a little salt and distilled white vinegar.
Add the potato strips and boil until they look slightly translucent but are not too soft.
Drain the potatoes, then rinse them again under cold running water. Let them drain well.
Add the granulated sugar and gently toss until the fries are lightly coated.
Sprinkle in the cornstarch a little at a time, tossing until each potato strip is evenly coated.
Heat the oil in a deep pot or deep skillet to about 325°F. Add the coated fries and let them cook for a little while before stirring so the coating can set.
Fry until lightly golden, then remove with a slotted spoon and drain.
Increase the oil temperature to about 375°F. Fry the potatoes again for about 30 seconds, or until extra crispy and golden brown.
Remove the fries and drain on paper towels. Serve hot.
