Like many skills in cooking, making a classic Hollandaise is simple after you do it a few times or have good luck, but frustratingly difficult if it goes wrong and you don't know why. One of the dishes we made many times in the last week or so of our Level 3 class at school was topped with Hollandaise, and for some reason our class had a much higher than normal rate of failed Hollandaise sauces. We made Hollandaise a few times in our Level 1 and Level 2 classes, and it was something that at first I got lucky with, and then later I began to struggle with it. Then our assistant chef was watching me make it one night, and walked over and said, "You're just whisking. You don't ever just whisk a Hollandaise." Once I figured out what he meant, I understood the process of Hollandaise, and I've not had much difficulty with it since. But before I get to that, let's look at what a Hollandaise sauce is.
Hollandaise is an "emulsion," which is a smooth and homogeneous mixture of two liquids that normally cannot be mixed, like oil and water, or in the case of a salad dressing, oil and vinegar. If you whisk oil and vinegar together into a smooth, creamy, cloudy emulsion, and then leave the mixture on the counter, it will usually separate pretty quickly, often in just a minute or two, and nearly always within twenty or thirty minutes. Some substances will help stabilize an emulsion when they are added to the mix, and they are called "emulsifiers." Generally they are long molecules that have a fat-soluble structure on one end, and a water-soluble structure at the other end. (Soap is an example of such a substance, and that's why water can remove grease when you add some soap to it.) Mustard and honey are moderately effective emulsifiers -- adding them to your salad dressing mix will make it hold together longer. But the strongest emulsifier we commonly use in food preparation is egg yolks.
When we make emulsions from egg yolks, we usually begin by whisking the egg yolks with a little bit of liquid for a few minutes before beginning to add any oil. Whisking the yolks causes the protein molecules to "unwind" from the curled-up ball shape they often have in a liquid into long straight strands which both exposes their fat- and water-soluble components and allows them to better coat the droplets of oil when we begin introducing it. In the case of Hollandaise, the sauce is cooked because it is a warm sauce, but also because heating helps to more permanently unwind the proteins and keep them from winding back up like little round springs. But we don't want to get it too hot, or the eggs will scramble (the fancy way to say this is that the proteins "coagulate").
The classic way to make Hollandaise is this: In a bowl over a hot water bath, whisk egg yolks and a couple tablespoons of water until they have a consistency like a cake batter. Then begin adding clarified butter, at first just a few drops at a time, whisking each addition until it is completely smooth and emulsified, with no sign (such as a thread-like dark streak where you whisk) of unemulsified oil. You can add just over a half cup of clarified butter per egg yolk. When finished, the sauce is seasoned with lemon juice, salt, and maybe a bit of cayenne pepper.
The challenge to Hollandaise is that you must keep it in a fairly narrow temperature range as you make it: below about 100F, the sauce will separate because the butter will start to solidify; a little above 150F, the egg yolks will begin to coagulate and can no longer coat the oil droplets. Fifty degrees sounds like a fair amount of leeway, but if you think about how your home stove probably keeps water simmering at about 200F even on its lowest setting, you'll realize that warming something to such a low temperature on the stove and holding it there while you work with it for ten minutes or so is not always easy. (Mayonnaise is basically the same sauce, made at room temperature using oil instead of butter, which gives it a less rich flavor, but makes it much easier to make.)
Chef Matthew and Just Whisking
One night a few months ago, as we were making Hollandaise, our assistant Chef Matthew walked up to me, and in his typically inscrutable manner demanded of me, "What are you doing?" I knew that in some sense I was busted, but I really didn't know what for, so I stood there looking at him for a moment, still whisking, with a deer-in-the-headlights look, waiting for him to throw me a hint about what kitchen crime I had committed this time. Then he said, "You're just whisking." I stood there even more unsure what he meant, still whisking but now a little more slowly since my chef seemed to be indicating that wasn't such a grand idea, and thinking to myself, "It's Hollandaise, of course I'm whisking!"
Eventually, after a bit of discussion, I finally understood what he was trying to tell me. During most of the time you spend making Hollandaise (after the initial heating of the eggs, and before the final flavoring with lemon juice, salt, and cayenne pepper), you should be always be doing at least one of these three things to the sauce: adding more butter, heating it because it has gotten too cold (most easily done by stirring in a spoonful of hot water from the water bath), or cooling it because it has gotten too hot (again most easily by adding a spoon of cold water). If you aren't doing any of those, then you can stop whisking (but don't leave your sauce over the heat if you stop), and take a moment to figure out which of those you ought to be doing. Most of us are so uncertain about whether the sauce is about to "break" that we keep whisking and whisking as though if we stop the whole thing will fall apart. But the point of using the egg as an emulsifier is that as long as the sauce is not too cold or too hot, and does not have more fat in it than the egg yolks can handle, it is really quite stable, at least enough that you can leave it sitting still in a warm place for ten minutes at a time.
When many people in our class were fighting with their Hollandaise in Level 3, someone asked our assistant chef, Chef Ryan, whether he noticed why our sauces breaking (whether we were usually getting them too hot or too cold or adding fat too fast). He said that he really hadn't seen what led to the sauces falling apart, and then added, "By the time I come over, usually you're just standing there whisking and hoping that whisking hard enough will magically fix it." No amount of whisking will bring a broken sauce back together. But his remark underscored for me the lesson that Chef Matthew taught me several months ago: Hollandaise is not about whisking, it's about controlling temperature while you incorporate more fat into the emulsion. Whisking happens to be the way you do both of those things.
Chef Hervé's Simple Hollandaise
One night when our Level 3 chef, Chef Phil, was absent, we had a substitute, Chef Hervé. He saw how many people were having problems with the Hollandaise, and at the end of the night he demonstrated a very simple way to make a Hollandaise in just three or four minutes. He whisked some eggs briefly directly on a burner with a very low flame, then added all of the butter at once, but very cold, directly out of the refrigerator. Then he raised the heat just a bit, and whisked madly for about three minutes, at the end of which he had a beautifully smooth and stable sauce. People were so impressed with the simplicity of his method that at the beginning of our next class, they asked our Chef Phil if they could make the sauce that way. He said that as far as he was concerned, any method that gave us a good Hollandaise was fine with him, but that we should know how to make it in the classic way because if we were ever asked by a chef considering us for a position in a restaurant to make a Hollandaise we would most likely be expected to make it the "right" way. He also warned us that just because Chef Hervé made his way look easy, we shouldn't expect that it would magically work for us any better than the classic method. Several people subsequently learned how true that is.
Ultimately, no matter how you make the sauce, the process will be the same: you must form an emulsion by mixing a very small amount of melted butter into egg yolks, and then slowly incorporate the rest of the butter into the sauce. Chef Hervé's method does not change this fundamental process: even though it looks like you're whisking all of the butter in at once, in reality you are only whisking in a little bit at a time, in the form of the part of the butter that has melted at any given moment while you whisk. In a way, Chef Hervé's way of making the sauce requires more skill, because where the classic way allows you to work on adding butter or control temperature separately from each other, Chef Hervé's simpler approach forces you to constantly add butter as it melts, it constantly cools your sauce as the cold butter melts into it, and it forces you to constantly heat the sauce to counteract that cooling. On the other hand, once you master the technique, his quick Hollandaise technique gives you an easy way to monitor and control the variable that most often derails you, which is the temperature of the sauce. The temperature is easily observed by simply watching how fast your butter is melting.