Peel the potatoes. Cut into 6 mm / ¼" French fries using a serrated knife.

Keep cut fries submerged in a bowl of water to prevent them from going brown while you cut the remainder.

Transfer potatoes to a colander and rinse under tap water for 15 - 20 seconds.

Place fries in a large pot with 2 litres/quarts of cold tap water, vinegar and salt. Bring to a boil over high heat, then immediately reduce stove to low.

Cook for 10 minutes then carefully remove using a slotted spoon into a colander.

Spread the fries on 2 tea towel lined trays. Leave to steam dry for 5 minutes.

Pour 3 cm / 1.2" of oil in a pot that is at least 10cm/4" high.

Separate the fries into 3 Batches.

Heat oil to 205°C/400°F over medium high heat.

Lower ⅓ of Batch 1 fries into the oil using a slotted spoon. WAIT 10 seconds, add another ⅓ of the fries, wait 10 seconds, then add the remaining Batch 1 fries.

Fry for 50 seconds, moving them around once or twice. Then remove with a slotted spoon onto 2 paper towel lined trays.

Repeat Fry #1 with Batches 2 and 3, ensuring the oil is back at 205°C/400°F before cooking.

Leave fries to cool for 30 minutes.

Line a large bowl with paper towels for draining and tossing.

Heat oil to 205°C/400°F. Fry half the French fries for 4 minutes until golden brown and crispy.

Drain in the lined bowl, then repeat with remaining fries.

Sprinkle fries with salt or seasoning of choice. Toss and serve!

Fries will stay crispy even once cool.