Since french fries essentially only need three core ingredients — potatoes, oil, and salt we wanted to know which potato the deep-frying experts turn to when they make their own version.

Sainsbury's French Fries cost £1.30 for 900g, which worked out to £1.44 per kilogram. They are made from 95 percent potato ... protein and 0.45g of salt. The packet said they needed 20 minutes ...