Slice potatoes into thin strips, then soak in cold water.
Bring the steak to room temperature then season generously with kosher salt and black pepper.
After frying, place the fries onto a paper towel-lined sheet pan.
Fry the French fries for a second time until crispy and golden brown, then drain.
Sear the steak. When ready, transfer to a plate, then rest and slice against the grain or serve whole.
Divide the steak between plates, sprinkle with flaky sea salt, then serve with heaping mounds of French fries on the side.