Make the sauce: In a small bowl, soak the ancho chile pepper in warm water to cover until soft, about 15 minutes. Drain, seed, and finely chop.

Peel, trim, and mince the garlic. Peel, trim, and chop the onion. Trim and dice the bell pepper. Peel, seed, and chop the plum tomatoes.

Heat the olive oil in a large skillet over medium heat. Add the garlic, onion, and bell pepper and cook, stirring, until the onion is translucent. Add the ancho pepper, tomatoes, chicken broth, and cayenne and bring the mixture to a boil. Cover, reduce the heat to low, and cook, stirring occasionally, for 30 minutes. Stir in the sherry vinegar and salt and pepper to taste and cook 5 minutes longer. Remove the pan from the heat and let cool.

Prepare the court bouillon for poaching the cod: Wash and slice the leek; rough-cut the carrot and fennel. In a nonreactive, deep skillet, combine the water, wine, leek, carrot, fennel, parsley sprigs, coriander seeds, peppercorns, bay leaves, and salt. Bring the mixture to a boil, lower the heat, and simmer for 20 minutes.

Meanwhile, cut the cod fillets into 6 equal portions. Add the cod to the simmering liquid and poach it gently for 10 to 12 minutes, or until the fish flakes easily when tested with a fork. With a spatula, remove the cooked cod to a serving platter. Discard the court bouillon.

Remove the leaves from the parsley sprigs and mince. Spoon the Catalan sauce over the cod fillets and sprinkle the chopped parsley over it. Best served within 1 hour of finishing.