Monter au Beurre

Literally “to work up with butter,” the expression monter au beurre refers to whisking whole butter into small amounts of concentrated liquids to create a sauce. Beurre blanc is the best example of this technique, but you can finish virtually any flavorful liquid with butter to convert it into a sauce. When finishing a sauce with butter, keep in mind that butter is a fragile emulsion that if mishandled will separate into fat, water, and proteins. To prevent the emulsion from breaking apart, use whole unsalted butter and make sure it is cold. Whisk the butter in, a tablespoon or so at a time, while moving the pan back and forth over high heat. If you’re making a lot of sauce, add more of it at once. Keep whisking until the butter is incorporated and the sauce has the texture and flavor you like. Don’t let the sauce boil for more than 1 or 2 seconds or the butter will separate. Serve the sauce within 30 minutes of finishing it with butter; ideally, you should serve it sooner. (See also “Brown Sauces”.)