Bacalà al Pil-Pil

If not already desalted, submerge the salt cod in a large bowl of cold water in the refrigerator. Change the water every 8–12 hours for 48 hours. The fish is ready when a small piece tastes pleasantly salty rather than overwhelming. After desalting, remove the fillets from the water and pat them completely dry on multiple layers of paper towel, then leave them uncovered on a rack at room temperature for 20 minutes. This drying step is critical: surface moisture is the enemy of the emulsion — it will cause the gelatin to dilute into water rather than binding with the oil. Run your fingers over the skin; the fillets should feel dry and faintly tacky, not wet.

In a wide, shallow clay cazuela or heavy skillet, combine the olive oil, sliced garlic, and dried chilis over the lowest possible heat. When the garlic begins to sizzle gently (about 2 minutes), nestle the cod fillets in skin-side up. The oil should never bubble aggressively — it should hover around 60–70C / 140–160F, which is well below a fry. Cook for 12–15 minutes, periodically tilting the pan to baste the fish with the warm oil. You will begin to see small white droplets forming at the edges of the fillets — this is the gelatin leaching from the fish into the oil. This is the raw material for the emulsion. When the fish is just cooked through and beginning to flake, gently remove the fillets with a slotted spatula onto a warm plate. Reserve every drop of the oil with its garlic and gelatin droplets.

This is the defining technique of the dish. With the reserved warm oil still in the pan over the lowest heat, begin moving the pan in slow, continuous circles — tilting it forward, sideways, backward, in a hypnotic, patient swirl. Do not stir, do not whisk. Just swing the pan. As you do this, the gelatin droplets begin to bind with the olive oil, and after 5–10 minutes a pale, creamy emulsion starts forming at the edges of the pan and slowly spreading to the center. The sauce goes from oily to ivory-white and slightly thickened, like a very loose aioli. If at any point it looks like it's about to split — the oil separates from the white mass — add a teaspoon of cold water and slow down the swirl. Taste and adjust salt very carefully. A pil-pil sauce that holds is one of the great quiet miracles of the kitchen.

Gently lower the reserved cod fillets back into the emulsified sauce, skin-side up, and tilt the pan to baste them with the sauce. The residual heat of the sauce will warm the fish through without further cooking. Taste the sauce carefully and add a pinch of salt only if needed — the fish and oil will have already contributed significant salt. To serve, bring the cazuela directly to the table. Tear crusty bread and drag it through the ivory sauce. The dish should be served warm, not hot — pil-pil breaks at temperatures above 80C, so never return it to a burner at this stage.