Finicky beurre blanc can be forgiving

If you have ever eaten fish in a restaurant, chances are you’ve also eaten beurre blanc sauce, because it is the perfect complement to fish. French for “white butter,” beurre blanc is simply butter flavored with wine, shallots and herbs, and, with the help of a few small tricks, is easy to prepare.

Beurre blanc is an emulsified sauce, which means that its fat is suspended in the watery liquid; an emulsion – such as hollandaise or mayonnaise – combines ingredients that would normally separate into disparate parts and forms them into a creamy whole that holds together and coats the food. Emulsified sauces are as temperature-sensitive as Goldilocks: too hot (200 degrees), and they’ll separate; too cold, and they’re done for. (So make it and enjoy it, but don’t try to save it.) That’s because butter itself is an emulsion of fat, milk solids and water; when butter is melted, it separates and the fat rises to the top, leaving a milky whey at the bottom. Once butter is melted, it cannot be re-emulsified. A trick for holding warm sauces so that they are still perfect at the time of service is to place them in a thermos. But please make sure that your beurre blanc thermos has never been used for coffee!

First-time sauce-makers look at a beurre blanc recipe in horror: It calls for a half-pound of butter! Yet this sauce tastes extremely light and delicate on the tongue. Unlike flour-thickened sauces, such as béchamel – which have a tendency to taste thick, goopy and heavy – butter-based sauces have a creamy lightness that allows the added herbs and seasonings to shine.

Beurre blanc is the perfect accompaniment for fish, because lean, dry fish need a good dose of butter to taste better. But don’t limit this classic to fish; it is also wonderful on chicken or vegetables. To make beurre blanc, bring a cup of white wine to a boil. Flavor the wine with minced shallots, whole peppercorns and a sprig of a fresh herb. Let the wine boil until the volume is reduced to a couple of tablespoons. Strain out and discard the solids. Though it’s not the traditional method, many cooks add a tablespoon of heavy cream to help stabilize the sauce. Over low heat, whisk in a cup of cold butter, a tablespoon at a time. The temperature of the butter is critically important; the butter must be refrigerator-cold or else the sauce will easily collapse and separate.

That said, beurre blanc is also very forgiving; unlike a mayonnaise, the cook can add more or less butter than the recipe calls for. When a cook adds oil to eggs to make mayo, the addition is 100 percent fat. But since most butter is only 80 percent fat, there is no limit (other than taste) on how much butter can be whipped into the reduction.

Now the fun part: flavoring the sauce. The possibilities are endless. Chopped fresh herbs (such as dill, tarragon or oregano) are especially delicious. Citrus is a wonderful complement; use a microplane rasp to grate the lemon, lime or orange zest into the sauce. Adding capers or minced anchovies is always a good idea, and even pesto or a tomato purée can be added. When red wine is substituted for white wine, the sauce is called beurre rouge. The pink sauce looks fabulous on fish and brightens the plate presentation. My favorite beurre rouge sauce is made with a local port wine and is served with Missouri trout.

Anne Cori, a Certified Culinary Professional, has taught cooking classes for more than 15 years at Kitchen Conservatory.