Cod Donostiarra style: Traditional Broth Recipe

What is Bacalao a la Donostiarra

Bacalao a la donostiarra — literally, "San Sebastián style cod" — is a preparation that defines the cuisine of the Gipuzkoan capital. It originated in San Sebastián's gastronomic societies, those txokos where members cook together and friendly compete over who prepares cod the best.

The recipe is based on a simple but difficult-to-execute principle: slowly cooking cod in olive oil with sliced garlic, and then creating a soupy sauce by emulsifying the oil with fish stock and the gelatin released by the cod itself. The result is a soupy, comforting, and deeply flavorful dish — a dense, silky broth that envelops the cod like a blanket.

In San Sebastián, every txoko and every restaurant has its version. Some add chili, others incorporate a light sautéed onion, some mount the sauce in the same pan and others do it separately. But the spirit is always the same: cod, garlic, olive oil, and patience to achieve that soupy emulsion that is the dish's signature.

Donostiarra is Basque comfort food at its finest. If pil pil is a dish of technique and precision, donostiarra is a dish of generosity and warmth. It is served in an earthenware casserole, with crusty bread for dipping, and shared at the table with an iced txakoli.

Donostiarra vs. Pil Pil: Two Techniques, Two Results

The confusion between bacalao a la donostiarra and bacalao al pil pil is common, even among experienced cooks. Both share basic ingredients (cod, garlic, oil, chili) and both depend on an emulsion, but the technique and result are fundamentally different.

Pil pil is a thick sauce, almost like a hot mayonnaise. It is achieved by moving the casserole in a circular motion while the cod releases gelatin, which emulsifies with the oil. It contains no water or broth — the emulsion is pure gelatin + oil. The final sauce is dense, sticky, and greenish-yellow. It is a dish of pure technique.

Donostiarra, on the other hand, incorporates fish stock (fumet) into the oil. The emulsion is lighter, more liquid, more soupy. The cod swims in the sauce instead of being covered by it. The texture resembles a thick seafood broth, silky and full-bodied, but one that can be eaten with a spoon.

Both techniques require excellent quality cod, with a good proportion of gelatin. Icelandic cod is ideal because the cold-water species Gadus morhua has a high collagen content, which turns into gelatin when heated and forms the basis of both emulsions.

Ingredients

• 4 desalted cod loins (150-180 g each, with skin)
• 200 ml extra virgin olive oil (mild)
• 8 cloves garlic, peeled and thinly sliced
• 1 dried chili pepper (cayenne or choricero)
• 200 ml fish stock (homemade or good quality)
• Fresh parsley, chopped
• Salt (only if needed, cod is already salty)

The Fumet: Key to the Dish

A good fumet makes the difference between a decent donostiarra and an extraordinary one. You can make it quickly with the cod's own bones and trimmings: boil bones + onion + leek + bay leaf for 20 minutes, strain, and done. If you don't have bones, a good quality fish stock in a glass jar (not stock cubes) is an acceptable alternative.

Do not use chicken or vegetable broth. Fish fumet has natural gelatin that helps with the emulsion. A broth without gelatin will result in a watery rather than silky sauce.

About Cod Skin

It is essential that the cod has skin for this recipe. Cod skin is rich in collagen, which turns into gelatin during cooking and is the natural emulsifier that binds the oil with the broth. Without skin, the emulsion does not form correctly, and you will have separated oil and broth instead of a uniform sauce.

Step-by-Step Recipe

Step 1: Brown the garlic and chili

In a wide earthenware casserole (or a deep pan), pour the 200 ml of olive oil and heat over medium-low heat. When the oil is warm (not hot), add the sliced garlic and the chili pepper broken in half.

Cook the garlic slowly, stirring, until light golden. This takes 3-4 minutes. It's important not to burn them — burnt garlic will bitter the entire sauce, and there's no way to fix it. When golden, remove the garlic and chili with a slotted spoon and set aside on a plate. The oil remains flavored in the casserole.

Step 2: Cook the cod

Lower the heat to minimum. Place the cod loins in the casserole with the skin facing up. This is counterintuitive but fundamental: skin facing up allows the gelatin to release directly into the oil, which is underneath.

Cook over very low heat for 8-10 minutes. The oil should not bubble — if it does, the heat is too high. The cod should cook slowly, almost confiting. You will see it begin to release a white, gelatinous substance: this is the key to the emulsion.

Step 3: Flip and add the fumet

Carefully, flip the loins (skin down now). Heat the fish fumet in a separate saucepan until hot (not boiling).

Pour the hot fumet into the casserole, around the cod, not directly on top. The liquid should cover about half of the loin. You will see the oil and broth begin to mix.

Step 4: Create the soupy emulsion

Here is the key technique of the dish. With the casserole over low heat, move the casserole with a back-and-forth motion, holding it by the handles. This movement, gentler than the circular motion of pil pil, gradually mixes the oil with the broth and the cod's gelatin.

You can also help with a wooden spoon, gently stirring the liquid around the cod (never over it, as it will break). Little by little, in 5-7 minutes, you will see that the broth and oil stop being separated and form a single sauce: a thick, creamy liquid, pale white to yellow in color, slightly opaque.

When the sauce has that texture — creamy but still liquid, like a light seafood cream — the emulsion is ready. Return the browned garlic and chili to the casserole.

Step 5: Finish and serve

Taste the sauce and adjust salt if necessary (remember cod already provides salt). Sprinkle fresh chopped parsley generously on top.

Serve directly in the earthenware casserole, bubbling, with crusty bread on the side for dipping into the sauce. Bacalao a la donostiarra is eaten with a spoon — the soupy sauce is as much a star as the fish.

The Soupy Emulsion Technique

The emulsion is the soul of donostiarra and what distinguishes this dish from a simple cod in broth. Understanding how it works will give you complete control over the recipe.

The cod's gelatin (mainly from the skin and the interstitial area of the flesh) acts as a natural emulsifier. When dissolved in hot liquid, its molecules interpose themselves between the oil droplets and the aqueous broth, preventing them from separating. This is exactly the same principle by which egg lecithin emulsifies mayonnaise.

For the emulsion to work, you need three conditions:

1. Low and constant temperature: Between 60-80°C. If it boils, the emulsion breaks because the violent movement of the water separates the phases. If it's too cold, the gelatin doesn't dissolve and won't emulsify.
2. Gentle and continuous movement: The back-and-forth motion of the casserole or spoon gradually incorporates the oil into the broth. Don't shake vigorously — the emulsion forms little by little.
3. Enough gelatin: Without cod skin, the emulsion is very difficult to achieve. If your cod doesn't have much skin, you can reinforce it by adding a dissolved sheet of gelatin (fish gelatin) to the fumet. It's not orthodox, but it works.

If the emulsion doesn't bind (oil and broth separate), carefully remove the cod and work only the liquid: lower the heat to minimum and move the casserole more insistently for 3-4 minutes. If it still doesn't bind, add a teaspoon of cornflour dissolved in cold water — it acts as an emergency emulsifier.

Accompaniments and Presentation

Donostiarra is a dish that requires few but well-chosen accompaniments:

• Crusty bread: It is mandatory. Loaf bread, thickly cut, lightly toasted. Used for dipping in the soupy sauce and is an integral part of the experience. Without bread, donostiarra loses half its charm.
• Boiled potatoes: Small boiled potatoes, added to the casserole in the last 5 minutes, so they absorb the sauce. It is the most traditional garnish of San Sebastián txokos.
• Peas: In season (spring), some fresh cooked peas added to the casserole add color and freshness to the dish.
• White asparagus: From Navarra, cooked and placed next to the cod. Its sweetness complements the intensity of the garlic.

The classic presentation is in the earthenware casserole itself, straight from the fire to the table. The earthenware retains heat and keeps the sauce bubbling throughout the meal. If you don't have an earthenware casserole, a preheated deep ceramic dish works.

Recipe Variations

Donostiarra has as many versions as cooks in the Basque Country. These are the most interesting variations:

• With confited onion: Some cooks add very finely chopped onion to the oil, before the garlic, and confit it until translucent. This adds sweetness to the broth and facilitates the emulsion (onion provides sugars that help bind).
• With choricero peppers: Hydrated choricero pepper pulp is added to the broth. It changes the color (from white to reddish) and adds a very interesting sweet and smoky depth. This is the "red donostiarra" version.
• With clams: Some versions incorporate clams that open in the broth just before serving. The clam juice greatly enriches the sauce and adds a touch of the sea that complements the cod.
• Extreme soupy version: Adding double the fumet (400 ml) results in an almost soup-like version. It is served in a deep bowl with a spoon and is perfect for cold winter days.

Whatever the variation, the essence is always the same: quality cod, garlic, olive oil, broth, and the patience to achieve that emulsion that transforms humble ingredients into an extraordinary dish.

Frequently Asked Questions