SERVES 4
Vizcaya is a Basque province, a maritime region with a dramatic coastline dotted with small fishing villages. (It is spelled Bizkaia in Euskera, the Basque language, and called Biscay in English. The region’s capital, Bilbao, is by far its largest city.) Its well-known red sauce—salsa vizcaína—is served with vegetables, snails, and fish, especially salt cod. The sauce’s main ingredient is the dried red pepper called choricero. There are also many excellent commercial brands that sell small jars of pasty choricero pulp (the labels usually read carne de pimiento choricero). Calculate about 2 teaspoons of paste per choricero pepper, or, for this recipe, about 3 tablespoons total.
1. Beginning 2 to 3 days ahead, desalt the cod following the directions on page 341. Do not remove the skin. Drain in a colander skin-side up for at least 1 to 2 hours. Pat dry with paper towels. There should be about 1¾ pounds/800 g of desalted fillets.
2. Cut the peppers open and remove the seeds. Put the peppers in a bowl, cover with at least 2 cups/480 ml hot water, and soak for 30 minutes. Drain, reserving the liquid. Using a coffee spoon, scrape the soft pulp from inside the skins and reserve. Discard the skins. There should be 3 to 4 tablespoons of pulp.
3. In a large skillet or sauté pan, heat 5 tablespoons of the olive oil over medium-low heat and add the onions, cooking until pale and tender, about 20 minutes. Add the garlic and cook until fragrant, about 1 minute. Stir in the pepper pulp and cook over medium heat for 5 minutes to concentrate the flavors. Stir in 1 cup/240 ml of the reserved liquid from the peppers and simmer until the onions are very tender, 5 to 10 minutes. Remove from the heat and let cool slightly. Pass the sauce through a food mill and then strain it through a conical strainer or chinois. The sauce should be fine and a bit loose. Stir in a bit more of the reserved liquid from the peppers if needed. Return the sauce to the skillet.
4. Meanwhile, in a clean skillet or sauté pan, heat the remaining 3 tablespoons olive oil over medium heat. Set the cod skin-side up in the oil and gently cook, only nudging from time to time to keep it from sticking, for 15 minutes. Transfer with a wide spatula to a plate with the skin side up.
5. Gently set the fish in the sauce, still keeping the skin side facing upward. Cook over medium-low heat in the sauce until warmed through, about 5 minutes. Serve immediately.