1.Cut potatoes into 5mm slices, then each slice into thin 5mm chips. Place chips in large bowl of cold water; stand 30 minutes. Drain; pat chips dry with absorbent paper.
2.Heat oil to 150°C on a deep-frying thermometer. (If you don’t have a thermometer, make sure the oil is not too hot for the first fry, you don’t want potatoes to colour.) Deep-fry the potatoes, in small batches, until cooked through but not coloured. Drain well, then place on absorbent paper.
3.Meanwhile, heat olive oil in large frying pan; cook steaks, in batches, until browned both sides and cooked as desired. Cover to keep warm.
4.While the steaks are resting, reheat the oil for deep-frying to 180°C, deep-fry the potatoes again, in batches, until crisp and golden. Drain well on plenty of crumpled absorbent paper.
5.Place wine in same frying pan as the steaks were cooked in; bring to a boil, stirring. Reduce heat; simmer, uncovered, 1 minute. Whisk in crème fraîche and mustard; simmer, uncovered, about 2 minutes or until sauce thickens slightly. Sprinkle the fries with salt and serve with steak and sauce immediately.
Sebago or bintje potatoes are best suited to this recipe.Note