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

Green sauce separates for one reason: temperature. Too much heat, too soon, and the oil separates from the broth. Arguiñano solves this by moving the pan, not by adding flour.

Here is the step-by-step recipe with real timings (15 minutes preparation, not the 30 others claim), the loin thickness that withstands cooking without falling apart (minimum 3 cm), the exact amount of parsley required by the original version, and the trick of the circular motion that thickens the pilpil without a blender or shortcuts.

Before the recipe, a note on the type of cod: not all types work. And the difference is noticeable in the dish.

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's one chef who has brought this recipe to millions of Spanish homes, it's Karlos Arguiñano. From his TV show, Arguiñano has prepared this dish countless times, always with the same philosophy: few ingredients, a lot 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." 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 unique flavor.

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

At Bacalalo, since 1990 in Barcelona's Mercat del Ninot, 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 (about 200g 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

For serving (optional)

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

How to make 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 cod trimmings and parsley stems.

Quick 20-minute broth

Place 600 ml of cold water in a pot 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 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 emulsion

The "vaivén" is the technique that makes green sauce what it is. It involves moving the pan with a continuous circular motion, as if you were rotating the contents inside. This constant movement emulsifies the oil with the broth and the cod gelatin, creating a thickened, 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 care." You don't stir with a spoon — you move the entire pan. A spoon would break the emulsion. The "vaivén" builds it.

Why does it work? High-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 fail, the sauce will not thicken correctly.

Step-by-step: complete cod in green sauce

Step 1: Prepare the loins

If using dried cod, desalinate 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 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 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 over — 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 (skin-side down) and sprinkle the tablespoon of flour over the oil, between the loins. Stir lightly to incorporate the flour.

Step 4: Deglaze with white wine

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

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

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

Keep the heat medium-low. The sauce should bubble gently, never boil vigorously. Continue the "vaivén" for 8-10 minutes. You'll see the sauce gradually thicken, transforming 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 "nappes" — that coats the back of a spoon without falling off immediately.

If the sauce is too thick, add a couple of tablespoons of broth. If it's too thin, continue with 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, blanch them and incorporate them in 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 is thickened by the "vaivén" of the pan, not with a spoon. Stirring with an utensil breaks the emulsion and the sauce will separate.
• 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 to retain their bright green color and freshness. If added at the beginning, they will darken and lose flavor.
• Warm broth: Adding cold broth to hot oil breaks the emulsion. Always use warm 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's 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