Clarified butter and vigilant whisking are the keys to this thick, sumptuous hollandaise sauce.

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.

Use clarified butter for a smooth sauce

Chefs differ on whether to use softened butter, melted butter, or clarified butter. Each has its merits and its flaws. Softened whole butter may have the most buttery flavor, but much of the airiness of the sauce will be lost because the butter will need more whisking as it's added to the sabayon. Melted butter also has a full flavor but will result in a thinner sauce because butter is about 25 percent water. If you want a thick sauce with the smoothest texture, clarified butter—butter with the water and milk solids removed—is your best bet.

After making the clarified butter (see the recipe), let it cool slightly before you add it to the sabayon. It should feel hot but not scalding; otherwise, it might break the sauce. Add the butter slowly and steadily, whisking all the while.

Clarified butter—which has the milk solids strained out—makes the thickest, smoothest sauce.

Add the butter a little at a time, whisking constantly. Be sure the butter isn't too hot or it will break the emulsion.

Holding and storing

Hollandaise and its sister sauces are best made close to serving. They can be kept warm for an hour in a covered saucepan in a hot—but not too-hot—water bath. You can also store the sauce overnight in the refrigerator. To reconstitute it, melt the sauce gently. Meanwhile, whisk an egg yolk with a tablespoon of water over medium heat until the yolk begins to stiffen. Gradually beat the melted sauce—it will look severely broken—into the yolk. The sauce should come back together but it won't be as light as the original sauce.