Scrub the russet potatoes thoroughly to remove dirt. Do not peel if you prefer skins on chips; otherwise peel. Using a mandoline set to 1.5–2 mm (about 1/16–1/8 inch) or a very sharp knife, slice the potatoes into very thin, even slices.

Rinse and remove surface starch

Place the potato slices into a large bowl and cover with cold water. Swirl gently to remove surface starch until the water runs mostly clear, about 2 minutes.

Soak

Fill the bowl (or transfer to another bowl) with fresh cold water and add the optional ice cubes or 1 cup ice to chill. Add 1 teaspoon vinegar if using (helps reduce browning and can improve crispness). Soak slices for at least 30 minutes and up to 2 hours in the refrigerator.

Dry thoroughly

Drain the potatoes in a colander and spread them out on clean kitchen towels or paper towels. Pat dry thoroughly—excess water will cause oil splatter and reduce crispness. You can also lay them in a single layer on a baking sheet and air-dry for 10–15 minutes.

Frying

Heat oil

Pour oil into a heavy, deep pot or Dutch oven to a depth of about 3–4 cm (1–1.5 inches). Heat the oil over medium-high heat until it reaches 180°C (355°F). If you don't have a thermometer, test by dropping one potato slice in: it should sizzle vigorously and rise to the surface.

Fry in batches

Working in small batches (about a handful of slices at a time, depending on pot size), carefully lower potato slices into the hot oil with a spider or slotted spoon. Stir gently to separate slices so they don't stick together. Fry until golden and crisp, 2–4 minutes per batch depending on thickness.

Drain

Use a slotted spoon to transfer chips to a wire rack set over a baking sheet or to paper towels to drain. Immediately while hot, sprinkle with a little fine salt. Continue frying remaining batches, maintaining oil temperature close to 175–180°C (350–355°F).

Final crisp (optional double-fry)

For extra-crispy chips, once all batches are lightly golden, increase oil to 190°C (375°F) and briefly return the drained chips to the oil for 30–60 seconds until deeply golden and very crisp. Drain again and salt immediately.

Seasoning & Serving

Season

After draining and while still hot, toss chips lightly with remaining fine salt and freshly ground black pepper to taste. For flavored versions, sprinkle smoked paprika and/or garlic powder and/or grated Parmesan and toss to coat evenly.

Cool and store

Let the chips cool completely on a wire rack to maintain crispness. Serve fresh. Store cooled chips in an airtight container at room temperature for up to 2 days; they will lose some crispness over time.