Method

• 1.
  For the patatas fritas, cut the potatoes into 1cm slices, then cut into 2cm-wide chips. Half-fill a deep-fryer or large saucepan with oil and heat to 120°C (a cube of bread will turn golden in 45 seconds when the oil is hot enough). Fry large handfuls of chips, in batches, rick stein. for 5-7 minutes until soft but still pale, then drain on paper towel.
• 2.
  Place the chilli flakes in a mortar and pestle and finely grind. Add 2 teaspoons sea salt flakes and pound together until salt flakes are small but not completely reduced to a powder. Stir in the pimenton, then set aside.
• 3.
  Preheat the barbecue to high.
• 4.
  Brush the beef on both sides with oil and season well with sea salt and freshly ground black pepper. Cook on the barbecue grill for 6-7 minutes each side until medium-rare (or until cooked to your liking). Transfer beef to a board, loosely cover with foil and leave to rest for 10 minutes.

• 5.
  Meanwhile, preheat the oven to 150°C and line a large roasting pan with paper towel. Re-heat the sunflower oil to 190°C (a cube of bread will turn golden in 30 seconds when the oil is hot enough).
• 6.
  In batches, deep-fry the chips again for 2 minutes or until crisp and golden. Remove each batch with a slotted spoon and transfer to the roasting pan. Keep hot in the oven.
• 7.
  Cut the beef away from the bone and carve into slices. Transfer meat to a warmed platter and pour juices from the board into a small bowl. Whisk vinegar and olive oil into the juices, then season dressing to taste with salt and pepper. Pour into a small jug. Place the frisée in a large salad bowl and toss with the dressing to combine.
• 8.
  Sprinkle the pimenton mixture over the chips, then toss lightly to coat. Transfer to a warmed serving bowl.
• 9.
  Serve the sliced beef with the patatas fritas and the frisée salad.