Peel and cut into four squares, then put to one side in olive oil. For the oil, soak the choricero peppers in tepid water.
Take the pulp and mix with 50 ml olive oil. Set aside.
Cut the leek into a fine julienne and fry in oil at 160 ºC until golden.
Drain on kitchen paper.
Peel the onions and cut into fine julienne.
Sprinkle with the sugar and then sauté in a hot frying pan until caramelised. Set aside.
Cut the cod into four parts, removing around one cm of meat from one side but keeping the skin. Wrap the black cod in its own skin and then sear in the frying pan, firstly where the skin joins to seal.
Cook for 2 minutes on each side on a low heat.
Serve with the roast pepper, the leek julienne, the caramelised onion and the choricero oil.