There's no denying the irresistibility of hollandaise sauce, especially one that's well made: thick yet airy, with a rich, buttery flavor brightened with a splash of lemon juice. Hollandaise, or its sister sauce Béarnaise, is wonderful at the holiday table, whether paired with poached eggs for a New Year's brunch or with beef tenderloin for Christmas dinner.
Making hollandaise can be tricky, however: it's easy to overcook, it can separate (break) for seemingly no reason, and it can turn out disappointingly thin or heavy and gluey. Knowing how to avoid these pitfalls—using the proper heat, getting the right ratio of eggs to butter, using clarified butter, and whisking to incorporate air—will go a long way toward making a successful sauce. It also helps to know that a broken sauce can be fixed.
Not one, but two emulsions
Whisk the eggs and water for 30 seconds off the heat. Lift the whisk high in the bowl as you work to whip lots of air into the eggs.
One reason hollandaise is challenging is that you're trying to coax together liquids that don't normally mix, making what's called an emulsion. First egg yolks and water are whisked together over heat to create a fluffy initial emulsion, which the French call a sabayon (not to be confused with a sauce sabayon, which is a dessert sauce). Butter is then slowly incorporated into the yolk-water emulsion, creating another emulsion.
Cook the sabayon over very low heat, whisking constantly and scraping the bowl, until thick and voluminous. The whisk will leave tracks that hold for a few seconds.
Cooking the sabayon can be tricky. Undercooking the sabayon results in a sauce that's too thin; overcooking it creates coagulated lumps. This kind of curdling can't be repaired. The good news is that if the sabayon does go awry, it's easy enough to start over with a few new egg yolks since you won't have wasted any butter yet.
Skip the double boiler for better heat control. Many hollandaise recipes suggest using a double boiler. I find that this offers a false sense of security since a double boiler offers no guarantee against overheating. Instead, I cook the sabayon directly over low heat.
A Windsor pan (a saucepan with sloped sides) works best for cooking the sabayon because the eggs aren't able to collect in the corner of the pan where, out of the reach of the whisk, they can easily overcook. A heavy-duty metal mixing bowl—you have to hold it on one edge with a kitchen towel—also works well.
Get ready to whisk a lot. A metal whisk is vital to making hollandaise sauce. Vigorous whisking protects the eggs from overcooking and incorporates air into the sabayon. Be sure to lift the whisk in the bowl to help accomplish the latter.