Authentic Belgian double-fried chips made from floury Bintje potatoes, traditionally fried in pure beef drippings (blanc de bœuf) for a glass-like crisp crust and cloud-fluffy interior.
Peel the potatoes and cut into uniform 1cm thick batons. Rinse in cold water to wash away surface starch, then dry completely and thoroughly in a clean kitchen towel (any moisture creates steam and reduces crispness).
Melt the beef dripping in a deep-fat fryer or heavy pot and heat to 150°C. Fry the potato batons in batches for 6 to 7 minutes until tender on the inside but pale and uncoloured on the outside. Lift out and spread on a tray to cool completely for at least 20 minutes.
Increase the fat temperature to 180°C. Lower the cooled pre-fried chips back into the sizzling fat for 2 to 3 minutes until puffed, blistered, and deep golden brown.
Dump the smoking-hot frites into a paper-lined bowl, toss vigorously with sea salt flakes so the crunch echoes, and serve immediately in paper cones with rich Belgian mayonnaise.