Peel the 4 potatoes and cut lengthwise into 1/4-inch-thick sticks or slabs. Toss in a large bowl and add enough cold water to cover. Stir in a pinch salt and the vinegar and soak for at least 30 minutes or up to overnight.Drain the potatoes and then pat them as dry as possible. Put the potatoes in a Dutch oven or deep pot and pour in enough oil to cover them. Place over medium-low heat and cook until the potatoes are very tender, about 45 minutes.

Raise the heat to medium and cook, stirring gently if you’d like, until the fries are nicely browned, another 15 to 30 minutes.Place a folded paper bag or several layers of paper towels near the stovetop. Using a slotted spoon or tongs, remove the fries from the oil, letting as much of the oil drip back into the pot as possible, then spread the fries on the paper bag or towels to drain. Season with salt while still hot and serve immediately with sauce, chutney or tea.