Cod in Green Sauce Arguiñano Style: Basque Recipe Step by Step

Arguiñano and green sauce: the essence of Basque cuisine

If there is one dish that defines Basque cuisine, it's cod in green sauce. And if there is one chef who has brought this recipe to millions of Spanish homes, it's Karlos Arguiñano. From his television program, Arguiñano has prepared this dish countless times, always with the same philosophy: few ingredients, lots of technique, and exceptional produce.

Green sauce is not a cooked sauce in the traditional sense. It is a cold emulsion formed by moving the pan with a constant rhythm — what Basques call the "vaivén." The olive oil infused with garlic and parsley mixes with the fish broth and the gelatin released by the cod itself, creating a thickened, bright green sauce with a flavor unlike anything else.

This recipe is inspired by Karlos Arguiñano's style, adapted with premium quality Icelandic cod. We do not intend to reproduce his exact recipe, but rather to capture the essence of his approach: simplicity, respect for the product, and the joy he conveys while cooking.

At Bacalalo, since 1990 in Mercat del Ninot in Barcelona, we select Icelandic cod that has the perfect texture and collagen content for the green sauce to thicken naturally. Because without good cod, there is no good green sauce.

Ingredients for cod in green sauce

For 4 people

For the cod

• 4 Icelandic cod loins (approx. 200 g each, desalted)
• Flour for dusting

For the green sauce

• 6 cloves of garlic, thinly sliced
• 1 large bunch of fresh parsley (leaves and stems separated)
• 150 ml extra virgin olive oil
• 100 ml dry white wine
• 400 ml fish broth (homemade or good quality)
• 1 tablespoon flour (optional, to help thicken)
• Salt

To accompany (optional)

• 8-12 green asparagus spears
• 200 g fresh or frozen peas
• 4 clams per person (optional)

Prepare a quick fish broth

Green sauce needs a good fish broth. If you don't have homemade broth, you can make a quick one with the cod trimmings and parsley stems.

Quick 20-minute broth

In a pot, place 600 ml of cold water with the parsley stems, half an onion, a crushed garlic clove, and, if you have them, some white fish bones or skins. Bring to a boil, reduce the heat, and cook for 15-20 minutes. Strain and set aside.

Arguiñano insists that fish broth should never boil vigorously — a gentle simmer, with barely visible bubbles, extracts flavor without making the broth cloudy or bitter. It's one of those details that seem minor but make all the difference.

The "vaivén" technique: the secret to the emulsion

The "vaivén" is the technique that makes green sauce what it is. It consists of moving the pan with a continuous circular motion, as if you were rotating its contents. This constant movement emulsifies the oil with the broth and the gelatin from the cod, creating a thick, creamy, and shiny sauce without the need for cream, butter, or thickeners.

Arguiñano always explains it with the same image: "You have to move the pan as if you were rocking it, with affection." You don't stir with a spoon — you move the entire pan. The spoon would break the emulsion. The "vaivén" builds it.

Why does it work? Good quality Icelandic cod is rich in collagen. When cooked over low heat, this collagen dissolves into the broth and acts as a natural emulsifier — exactly the same principle that makes pil pil work. The circular motion helps the oil droplets disperse evenly in the gelatinous broth, creating that characteristic silky texture.

For the "vaivén" to work, you need three things: enough oil, full-bodied fish broth, and cod with collagen. If any of the three fails, the sauce will not thicken properly.

Step by step: complete cod in green sauce

Step 1: Prepare the loins

If using dried cod, desalt it in cold water in the refrigerator for 48 hours, changing the water every 8-10 hours. If you buy pre-desalted cod, go directly to the next step. Pat the loins dry with kitchen paper and dust them lightly with flour, shaking off any excess.

Step 2: Infuse the oil with garlic

In a wide, shallow pan (an earthenware casserole is ideal), pour the 150 ml of olive oil and heat over medium-low heat. Add the sliced garlic and cook very slowly for 3-4 minutes, until pale golden. If the garlic burns, discard it and start again — burnt garlic will bitter the entire sauce.

Step 3: Place the cod and add the flour

Increase the heat slightly to medium. Place the cod loins in the pan skin-side up. Cook for 1 minute on that side. Flip them over (skin-side down) and sprinkle the tablespoon of flour over the oil, between the loins. Stir lightly so the flour incorporates.

Step 4: Deglaze with white wine

Pour the white wine over the loins. Let it bubble and the alcohol evaporate for 1-2 minutes. The wine adds acidity and depth to the sauce.

Step 5: Add the broth and start the "vaivén"

Pour in the lukewarm fish broth (never cold, to avoid breaking the emulsion). The liquid should cover the loins up to half their thickness — if not enough, add a little more. Now begin the "vaivén": grasp the pan by the handle and move it with a continuous circular motion.

Maintain medium-low heat. The sauce should bubble gently, never boil vigorously. Continue the "vaivén" for 8-10 minutes. You will see how the sauce gradually thickens, changing from a clear liquid to creamy and bright green.

Step 6: Add the parsley

When the sauce begins to thicken, add the very finely chopped parsley leaves. Continue with the "vaivén" for 3-4 more minutes. The sauce should have a consistency that coats the back of a spoon without immediately running off.

If the sauce is too thick, add a couple of tablespoons of broth. If it is too thin, continue the "vaivén" a little longer — the reduction and gelatin will do their work.

Step 7: Serve immediately

Green sauce is served freshly made, directly from the pan to the plates. If adding asparagus or peas, incorporate them blanched during the last 3 minutes of cooking. If using clams, open them separately in a pan with a little white wine and add them at the end as a garnish.

Arguiñano's tips for the perfect green sauce

• Never stir with a spoon: Green sauce thickens with the "vaivén" of the pan, not with a spoon. Stirring with an utensil breaks the emulsion and the sauce will split.
• Garlic golden, never burnt: Sliced garlic should be cooked over very low heat until pale golden. Burnt garlic will irreversibly bitter the entire sauce.
• Parsley at the end: Parsley leaves are added in the last few minutes so they retain their bright green color and freshness. If you add them at the beginning, they darken and lose flavor.
• Lukewarm broth: Adding cold broth to hot oil breaks the emulsion. Always use lukewarm or room temperature broth.
• Constant medium-low heat: Green sauce should never boil vigorously. Aggressive boiling breaks the emulsion and toughens the cod.
• Cod with collagen: The gelatin from the cod is the natural emulsifier for green sauce. Quality Icelandic cod, with good thickness and collagen content, makes the sauce thicken effortlessly.
• Serve immediately: Green sauce doesn't wait. It is served freshly made, directly from the pan to the plate. If it cools, it can be gently reheated with the "vaivén," but it will never be the same as freshly made.

Frequently asked questions