Bacalao al Pil Pil

Bacalao is salted, dried cod; pil pil is the amazing Basque sauce that is created by the addition of olive oil, which is whipped into a Hollandaise to Mayonnaise-like creamy texture.  In this post, I'll share a modernist technique we learned at the Smithsonian Folklife Festival's Basque food demonstrations: it's much more reliable than older procedures we've tried. This will be a fairly detailed post because I want you to be successful when you make it -- it was a revelation to us.

Background

I've written about my love for Bacalao elsewhere in this blog. While popular in the Nordic countries, Portugal and Italy, I've mostly had Spanish bacalao dishes -- specifically from Catalunya and the Basque country. It's got a firm texture and slight funk that I like.

But what I'm really excited about is the pil pil sauce, and how it's different from it's more famous emulsified cousins. What's cool about pil pil is that it needs no added emulsifier to make it thick and stable.

Emulsions

An "emulsion" is a mixture of two or more liquids that normally won't stay together as one. An oil and vinegar salad dressing is one example: it's unstable -- you have to shake it to get them to mix, and if you let it sit, the oil and vinegar will separate.

An "emulsifier" is an ingredient that will help the separable liquids combine in a stable way. In a Hollandaise sauce, the egg yolk keeps the water and fat in the butter together in a sauce. In Mayonnaise, egg yolk does the same for the oil, vinegar and lemon juice. In the Mediterranean, Aioli sauce uses just garlic as an emulsifier to make a sauce from of olive oil; this is a more difficult sauce to make as garlic has less emulsifying power than yolks. Less commonly, paprika can be used as an emulsifier. The food industry has developed plenty of concoctions used as emulsifiers.

In pil pil sauce, there is no egg yolk, no garlic, no other emulsifier. Everything needed to thicken the sauce comes from the fish itself -- pretty cool!  My understanding is that there are proteins between the skin and flesh of bacalao that act as emulsifiers when leached out as part of the cooking process: every recipe for pil pil I've seen says you must use skin-on bacalao, presumably for this reason.

Science vs. Grandmothers

Teresa Barrenechea's book, The Basque Table, describes the classic technique. After rehydrating and desalting the bacalao, it is simmered in water, then placed skin-side up in a earthenware casserole. A small amount of olive oil is added and the fish is swirled around in a circular motion through the oil until an emulsion forms. Oil is slowly added to the existing emulsion to build the sauce. As she says in the book, "Bacalao al pil pil is technically difficult to make, but not too hard for the home cook to master."

In my experience, it's exceptionally hard to get the emulsion to start; and there are many variables including the amount of heat to apply, whether to add a touch of water, when to add the oil, etc. We've left a lot of the clay from the bottom of our cazuela on our gas cooktop ring in the process of swirling for what seemed like an eternity. This technique, handed down from grandmother to grandmother, may be classic but there must be a better way -- we need to understand why the emulsion forms.

The Basque cooking demonstrations at the 2016 Smithsonian Folklife Festival finally revealed the secret: science!

Chefs Igor and Igor from Escuela Superior de Hosteleria Bilbao gave a great demonstration of this sauce.  After hydrating bacalao, they poached it skin-side up in olive oil for 10 minutes to cook it. They kept the temperature low so that they didn't boil off the precious juices that the cod exuded, which they called "gelatin"; I interpreted this to mean the liquid should never reach the boiling point of water. They also held the microphone to the pot and explained that the noise the small bubbles made was the origin of the name "pil pil"; there is some debate on this matter, but it seems as reasonable as any other explanation. They set the cooked cod aside and poured out the oil containing the gelatin and allowed it to settle out; they then separated the oil from the magical cod juice.

Chef Igor holds the separated cod gelatin with a layer of oil on the top. This is precious, "you can't buy it."

They then poured some of the white liquid into a pan on a very low heat and agitated it to start the emulsion by whipping some air into it. Instead of the grandmotherly technique using the fish itself, they used a small strainer, something that is great at whipping air into the liquid.  When the liquid started to set up a bit into a thicker consistency, they dribbled oil into it -- slowly at first then more rapidly once the sauce was well established. It worked beautifully.

Procedure

We got bacalao, skin on and without bones from a local Portuguese/Spanish shop. They have the dried bacalao but one kind had no skin and the other had bones; the skin-on boneless one was kept in the fridge, and had already been rehydrated so it was basically ready to use.  The 1.6 Kg was $28 so it's not cheap, but neither is fresh cod.

We defrosted it then put it in a pot, skin side up, and covered with good olive oil. We added some garlic cloves and a dried spicy chili, and set it on very low heat.

Because of the thickness of these cod loin sections, it required quite a bit of oil. We heated it very gently, ensuring the oil never came near the boiling point of water, which would evaporate the fish juice. Below, there are 4 cloves of garlic, but you can also see little globules of the gelatin coming out of the fish and falling to the bottom of the pot -- we knew we'd got it right at this point, science to the rescue!

Our cod loin was about 7cm/2.5in thick, about double that of the cuts the chefs used, so we cooked it 30 minutes to ensure the fish was thoroughly cooked through.  Fish is done when it's 50-54C/122-130F, so cooking it low is fine. We kept it below about 80C/182F and just watched in amazement as the fish continued to release more gelatin; check this 7-second video:

(In books, blogs and such we've read, chefs say that when fish exudes white protein it's just at the point of being overcooked. Brining, they say, helps prevent this.  We wonder if the "cod juice" we're obsessing over here is the very same protein liquid that others are trying desperately to prevent.)

We pulled the fish out of the oil and set it aside; it was cooked throughly enough that it threatened to break apart along the muscle fibers, perhaps a bit too long or hot.

We poured out the oil and liquid and let them separate, then extracted the gelatin; we weren't worried that it had some oil left on it -- the pil pil needs it.

We added all the cod gelatin to a pan that was barely heated -- again, we didn't want to evaporate the elixir.  We used a small, fine-mesh strainer to whip air into it. Miraculously, it started thickening a bit after just a couple minutes of agitation.

 

We drizzled a tiny bit of the fishy olive oil into the emerging sauce and watched it get absorbed and expand the sauce.

And then more oil, a little faster now:

Then more oil, without worrying much about how much we were adding:

It thickened to a Mayonnaise-like consistency. The color comes exclusively from the good olive oil we used, not eggs or other additives.

This may have been too thick for a classic pil pil, but it tasted intensely of olive oil -- including the slight cough-inducing bitterness -- and fish. A thick, stable sauce using only olive oil, in addition to liquid from the fish itself. Rather amazing.

We used some of the left over olive oil to poach baby potatoes, and sautéed home-grown shishito peppers with coarse salt and a bit more of the oil like we'd prepare Catalan Padrón peppers, and sliced and fried the cooked garlic cloves as a garnish.  There's quite a bit of thick pil pil sauce here:

It tasted intense, and worked miraculously -- no magic, no granny's secrets, just a great cooking technique.

What worked, what didn't

Poaching the cod in oil to extract the gelatin worked so much better than protracted pot-shaking. The strainer helped aerate the emerging emulsion.

The taste of the good oil really came through.

Our pil pil was probably too thick for the classic standard, more a Mayonnaise than a Hollandaise consistency.  We had used all the exuded cod gelatin, but probably could have used at most half, reserving the rest for our next adventure.

We had 2 cups olive oil left over. It's not going to waste, we can keep it from oxidizing by freezing it, and use it little by little.

Next Time...

We'd like to find a thinner cut of fish: it would require less oil to cover and cook more quickly.

Cook the fish less, ours was just barely holding together.

Use less cod gelatin, we'd like a less thick sauce and we'd like to use the extra fish juice to make pil pil for other dishes.

We could thin the sauce by adding a dash of lemon juice or white wine, but we wonder whether the ghosts of Basque grandmothers would haunt us to our graves.

Is it true that only bacalao can be used? That it has to be skin-on? In the pot, we saw bubbles of the liquid coming out of the core of the body of the fish, not just from under the skin; try it with:

• skin-on fresh cod.
• skinless cod, fresh or rehydrated bacalao
• skin-on sea trout which also has a thick layer of subcutaneous fat