Bearnaise sauce in a small bowl
Sauce béarnaise, the bolder cousin of hollandaise, can make ordinary food spectacular and great food into a fête.Photograph from Alamy

On a quiet summery Saturday evening several years ago, when I was living with my family in Lyon, my wife and I arranged a last-minute babysitter to look after our twin sons. Then we took off, got out of the city, and drove south along the Rhône, looking for a place for dinner. The roads were empty, and the light was a fading orange. We had no reservation and no plan except to keep driving until we found something. What we found, instead, was that every place we stopped at was raucously full. Twenty-five miles later, in Condrieu, a town famous for a luscious floral white wine made with the local Viognier grape, we spotted a hotel on the bank of the Rhône called Le Beau Rivage. We were surveying the dining room—there appeared to be only one table left—when a maître d’ greeted us and asked if we were guests, and we, by now hungry and distressed, abandoned scruples and said yes. We drank wine made from vines growing on the steep hills directly behind us and ate a surprising meal. The highlight was a massive turbot, the flat, shellfish-munching bottom-feeder whose eyes float arbitrarily on one side of its scaly, weird head (a special category of marine delicacy, fabulously ugly and fabulously delicious). It was carved tableside and served with a fluffy, pale-yellow sauce béarnaise, which wasn’t dribbled atop or poured over but seemed, rather, to settle alongside the fish like a perfumed, mysterious fog.

Until that evening, I hadn’t thought much about béarnaise. I had learned to make it as a culinary student at L’Institut Paul Bocuse, but I regarded it as just a thing people ate with Sunday roast beef. I’d never eaten it with fish. I’d also never tasted a version so perfectly rendered, with a vivid vinegar acidity that seemed to wrap itself around every molecule of the sauce’s fat. I liked, too, that it was different from most other French sauces, which are wine-based and can be manipulated to match the food they are served with. A béarnaise doesn’t have to match. It’s just there. It could be its own food group.

French cookbooks tend to regard a béarnaise as a no-brainer, but after our meal on the banks of the Rhône I found myself disappointed every time I ordered it at a restaurant, including on two return trips to Le Beau Rivage: it was unpleasantly heavy, overcooked, or thickened with flour, having been neglected during a busy service. And, for my part, I was only occasionally successful when I made it at home. Sometimes it worked, and I was happy. Sometimes it seemed to work, only to fall apart moments later. A failed béarnaise is a mess. Some describe it as scrambled eggs. It’s more like barf.

When I was working in a Lyonnais kitchen, I got another chance to make the sauce. The restaurant was La Mère Brazier, a Lyonnais institution; the executive chef was Christophe Hubert, and I was a stagiaire (something like an apprentice). My job included making the staff meal, le personnel. One day, I asked if I could make a béarnaise.

“No,” he said, flat out. “It is too difficult.” Hubert’s position was perfectly reasonable. He wanted to feed his staff. “Have you even made a béarnaise?”

“Yes.”

“Often?”

“No.”

“Then why make one now?”

“Because that is why I am here.”

He was confused.

“To learn. I am here to learn.” Je suis ici pour apprendre. It seemed obvious, but apparently it wasn’t. Hubert uttered a faintly audible “Huh.” He got it: I wasn’t going through an initiation rite to become a professional French chef. I was there to learn what a French chef does.

The following week, the protein was steak. Hubert gave me the go-ahead: “Make your sauce.”

“Ah, the perfume of the mignonette,” he said, once I’d got started. Mignonette describes the infusion—shallots, black pepper, and the licorice fragrance of tarragon in a bracing white vinegar, simmered slowly to extract the flavors.

The infusion is one of the three components of a béarnaise. The other two are egg yolks and clarified butter. Both béarnaise and its cousin hollandaise are at the heart of the French kitchen. Hollandaise, which may or may not have come from the Netherlands (akin to how a béarnaise may have come from Béarn but probably didn’t), is one of the five mother sauces that the chef and author Auguste Escoffier categorized as the fundamentals of French cooking. (The others are béchamel, velouté, tomate, and espagnole, the wonderfully intense veal-tomato combination that is said to have been conceived by a Spanish cook at the wedding of Louis XIII and Anne of Austria, in 1615.) Hollandaise and béarnaise are basically alike. Where they differ is in their acidity: a hollandaise is lightly enhanced with lemon, whereas a béarnaise is emboldened by that vinegar reduction. Some cooks cut the vinegar with white wine, but in Lyon, in my experience, the béarnaise is often made only with vinegar, and only with the most in-your-face version of it, white vinegar, which is derived not from wine but from grain alcohol and is used by housekeepers for cleaning. Béarnaise is a sauce that bites back. When done right, it makes ordinary food spectacular, and great food into a fête.

Béarnaise is an emulsion—made by getting two incompatible elements, liquid and fat, to bond. (Actually, the secret code of French cooking—its flair—seems always to involve getting two incompatible elements to live with each other.) It is unlike other emulsions (such as vinaigrette or mayonnaise) because it is cooked. Making a béarnaise involves adding your egg yolks to the reduction (which must be thoroughly cooled after simmering), heating them up slowly while whisking vigorously, and hoping to arrive at that awkward, custard-forming temperature that is precisely between raw and ruined. How hot? Well, according to the writer Harold McGee, it should be fifty degrees Celsius. But according to L’Institut Bocuse’s textbook it’s sixty degrees, and according to the chef Joël Robuchon it’s sixty-five degrees. The truth is that all these figures are useless, because you’re not about to poke a thermometer into your pot while you are wildly whisking away, afraid that at any moment the sauce might break. I use my finger, dipped quickly; if I burn myself, I know I’m in trouble.

In the béarnaise that I was making for the staff lunch, the egg yolks and the reduction frothed up impressively. I then introduced the last ingredient, a golden thread of clarified butter, whisking, whisking, whisking, as the sauce seemed to defy gravity and puff up. I tasted it. I added salt and pepper. I tasted it again. I added a bit of lemon. It seemed to be missing something.

Hubert tasted it. “What does it need?”

“Vinegar,” I said.

“Vinegar, really?” He looked at me, stupefied. The sauce already had a lot.

I added the vinegar, with Hubert looking powerfully doubtful. We tasted again.

“You were right,” he said.

It was a good moment. Then it was a bad moment. As we were standing there, the sauce broke before our eyes. I had failed. It was barf.

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