Bacalao al Pil-Pil: Four Ingredients and a Wrist

There are four things in a pil-pil pan — salt cod, olive oil, garlic, chilli — and at the end of it you have a pale yellow sauce with the body of a hollandaise. No butter, no cream, no flour, no egg yolk. Every gram of what holds it together came out of the fish.

I have watched people refuse to believe this while eating it. The suspicion is reasonable: an emulsion needs an emulsifier, and there is visibly nothing in the pan that looks like one. The emulsifier is gelatine, leached out of the collagen in the cod’s skin and the connective tissue just beneath it, and the entire technique is a set of rules for getting it out without cooking it to death.

Bilbao, 1836, and a clerical error

The story Basques tell is that in 1836, during the First Carlist War, a Bilbao merchant named Simón Gurtubay ordered 120 or 140 pieces of salt cod from a Norwegian supplier. The order was read as 120,040, and something like a million cod arrived on the quay. Bilbao was then besieged by Carlist forces, the city was starving, and Gurtubay’s absurd warehouse of dried fish fed it. He made a fortune. The dish, so the story goes, came out of the months that followed.

It is a good story and it is probably partly true and partly polished. What is certainly true is the underlying fact: Bilbao was a salt cod city. The Basques had been fishing cod off Newfoundland since well before Cabot’s 1497 voyage — there is a persistent, unresolved argument that Basque whalers and cod fishermen knew the Grand Banks and kept quiet about it — and salting the catch on the boat was how they got it home across an ocean without refrigeration.

Salt cod outlived its own necessity. Refrigeration arrived, fresh fish became trivial to get, and the Basques went on eating bacalao because they had spent four hundred years learning what it does that fresh cod cannot. Salting draws out water and concentrates the flesh, so the flakes are larger, firmer and more distinct, and the long cure develops savoury compounds that fresh cod simply does not have. It is a different ingredient with the same Latin name.

Pil-pil is onomatopoeia — the sound the oil makes when it is at exactly the right temperature, a slow, intermittent popping. The dish is named after a noise, which tells you where the attention is meant to be.

Buying the fish, and the pan to do it in

Buy loin. Salt cod is sold in graded cuts and the price gap between them is large, but the loin — the thick shoulder end, sometimes labelled lomo — is the only cut that gives you both the gelatinous skin and enough depth of flesh to survive the confit. Tail pieces are thin, desalt in a day, and are perfectly good in other dishes. Look for pieces that are creamy white rather than yellow; yellowing means the fat has oxidised and the fish is old, and old salt cod tastes of the cupboard it sat in.

The skin must be on. This is the one non-negotiable in the shopping. Skinless salt cod cannot make pil-pil, because the skin is where most of the collagen lives, and a skinless loin will give you a pan of hot oil and a mild sense of betrayal.

The pan matters more here than in most dishes. A cazuela de barro — glazed terracotta, wide and shallow, with two small handles — is what Basque kitchens use, and its virtue is thermal mass. Earthenware holds heat and releases it slowly, which makes the low, stable 60°C confit far easier to hit than it is on thin steel, where the temperature swings every time the flame cycles. It also gives you two handles to shake by. If you are buying one, season it first: soak it in water overnight, rub the inside with a cut garlic clove, and warm it through with oil in a low oven.

A heavy cast-iron or steel frying pan works. Set the flame lower than feels right and be prepared to lift the pan off the heat whenever the oil starts to whisper. Non-stick is the worst option — the coating and the shake are a bad match, and thin non-stick pans swing in temperature more than anything else in the kitchen.

Twenty-four centimetres is about the right diameter for two loins. Too wide and the 250ml of oil spreads thin and will not cover the fish; too narrow and you need more oil than the gelatine can carry, and the sauce comes out slack.

Desalting: 48 hours and a tasted flake

You cannot skip this and you cannot rush it. Proper bacalao salado comes stiff as a board and carries something like 20% salt by weight; it needs 36 to 48 hours in cold water in the fridge, with the water changed every eight hours.

Two details make the difference. Put the pieces skin side up: salt diffuses out downwards and settles at the bottom of the container, and a skin-side-down piece traps it against the flesh. And use plenty of water, at least four times the volume of the fish, because desalting slows to a crawl as the water approaches the fish’s own salinity.

Test by taste, never by clock. Tear a flake from the thin end and eat it. It should taste like a well-seasoned fresh fish. Under-desalted cod makes the sauce inedible; over-desalted cod is flabby and has lost the point. Thin tail pieces reach the mark in 24 hours and thick loins need the full 48, which is a good argument for buying loins and desalting them as a batch.

If you can only find bacalao already desalted at a fish counter, it will work, and it will have been done by someone with more practice than you.

The gelatine, the temperature, and the shake

Everything now turns on temperature, and every number below is doing real work.

Confit the cod at around 60–70°C. The oil should pop lazily and never sizzle. At this temperature the collagen in the skin and the sheet of connective tissue beneath it slowly converts to gelatine and seeps into the oil, while the muscle proteins set gently and stay juicy. Push the heat to a fry and the outside seizes, the gelatine stays locked in the skin, and you will end up with a pan of oil that will never emulsify no matter how long you shake it. This is the reason for every failed pil-pil I have ever seen.

Then you let the pan cool to about 40°C, and this is the step people skip. Gelatine and oil will not emulsify while the oil is hot — hot oil is too thin and too energetic, and the droplets simply coalesce back together as fast as you break them up. Cooled, the gelatine liquid thickens slightly and the oil gets more viscous, and the two will hold. Tip the pan at this point and you will see the milky white gelatine pooled underneath, which is your evidence that the confit worked.

The shake is a flat, continuous circular motion with the pan on the worktop. The traditional tool is a terracotta cazuela moved by both handles, and Basque cooks do it for five minutes without apparent effort while talking to somebody. What you are doing mechanically is shearing the oil into droplets small enough for the gelatine to coat and stabilise. It works. A sieve pressed flat and worked in circles works too, and is the standard cheat in Bilbao kitchens; so does a stick blender, though it makes a stiffer, paler sauce that purists can spot across a room.

If it splits or refuses, the rescue is the same as for mayonnaise. Pour off all but three tablespoons, emulsify that small volume — a small amount of oil against the same gelatine is a much easier ratio — and then dribble the rest back in a thin thread while shaking.

The garlic chips

Here is my small liberty, and it is a texture argument rather than a flavour one.

Most recipes fry the garlic and chilli to flavour the oil and then either discard them or drop them back into the sauce, where they go soft and slippery within a minute. I lift them out onto kitchen paper the moment they turn pale gold and let them crisp as they cool, then scatter them over at the very end.

Pil-pil is a soft dish. Flaking fish under a smooth emulsion, and nothing on the plate offers any resistance at all. The garlic chips give you a brittle snap and a burst of concentrated allium and heat against a sauce that is deliberately mild, and they land on top rather than dissolving into it. Pull them at pale gold — garlic goes from gold to bitter in about fifteen seconds, and burnt garlic in this dish is unforgivable, since one of your four ingredients has failed.

What goes wrong

The oil will not emulsify. Either the confit ran too hot and the gelatine never came out, or the oil is still too warm. Cool it to 40°C and try again. If there is no white liquid visible under the oil, the gelatine is not there and no amount of shaking will invent it.

The sauce is greasy and heavy. Too much oil for the amount of fish. Two loins want 250ml. Pour some off and re-emulsify.

Bitter, harsh sauce. A strongly peppery extra virgin olive oil. Pil-pil wants a mild, ripe, buttery oil — a fierce Picual will dominate everything.

Tough, dry cod. It fried instead of confiting, or it went too long. Ten minutes on the skin and three on the flesh is plenty for a 3cm loin.

Serving, and where else the skill goes

Serve it straight from the pan with bread and nothing else. Pil-pil is a starter or a small main; two loins feed two people who are having something afterwards. A cold Txakoli or a white Rioja.

It does not keep and it does not reheat — warming the sauce past 50°C splits it irreversibly, and there is no getting it back once the fish has been in the fridge.

The desalting skill transfers directly to bacalhau à brás, which is what to make with the tail pieces from the same batch. And the discipline of watching garlic in oil for exactly the right shade of gold is the same one that governs Castilian garlic soup — in both dishes, fifteen seconds of inattention costs you the whole pot.