Traditionally, beurre blanc is prepared as an integral part of the shallow- poaching process, using the reduction cooking liquid (cuisson). Another common practice is to prepare a reduction separately and make the beurre blanc in a larger batch so it can be used as a grand sauce on which derivative sauces are based. As with hollandaise, beurre blanc derivatives are prepared by either varying the ingredients in the reduction or altering the garnish ingredients. Beurre rouge, for instance, is made by using red wine in the reduction.
The quality of the butter is critical to the success of a beurre blanc. Unsalted butter is best because the salt level can better be controlled to taste later on. Check the butter carefully for a creamy texture and sweet aroma. Cube the butter and keep it cool.
A standard reduction for a beurre blanc is made from dry white wine and shallots. (When prepared as part of a shallow-poached dish, the cooking liquid becomes the reduction used in the sauce.) Other ingredients often used in the reduction include vinegar or citrus juice; chopped herbs including tarragon, basil, chives, or chervil; cracked peppercorns; and sometimes garlic, ginger, lemongrass, saffron, and other flavoring ingredients.
A small amount of reduced heavy cream is occasionally added to stabilize the emulsion. To use cream, reduce it by half separately. Carefully simmer the cream until it thickens and has a rich, ivory-yellow color. The more reduced the cream, the greater its stabilizing effect. The more stable the sauce, the longer it will last during service. However, the flavor of cream will overpower the fresh taste of the butter.
Be sure that the pan is of a nonreactive metal. Bi-metal pans, such as copper or anodized aluminum lined with stainless steel, are excellent choices for this sauce.
A whisk may be used to incorporate the butter into the sauce, but many chefs prefer to allow the motion of the pan swirling over the burner or flattop to incorporate the butter. Straining is optional for this sauce, but if you choose to strain either the reduction or the finished sauce, you will need a sieve. Once prepared, the sauce may be kept warm in the container used to prepare it, or it may be transferred to a clean bain-marie, ceramic vessel, or wide-necked vacuum bottle.
A basic formula for 32 fl oz/960 mL Beurre Blanc
1 lb 8 oz/680 g butter
Reduction made from: 8 fl oz/240 mL dry white wine3 fl oz/90 mL vinegar, shallots, and peppercorns, 4 fl oz/120 mL heavy cream (optional)
Ground white pepper
1. Prepare the initial reduction of acid, shallots, and peppercorns, which gives the sauce much of its flavor. Other aromatics, such as shallots or bay leaves, may be added as required by the recipe. Combine the reduction ingredients and reduce over fairly brisk heat to a syrupy consistency (à sec). If preparing the sauce as an integral part of a shallow-poached dish, simply reduce the cuisson. Reduce the heat to low. Gradually incorporate the butter into the reduction, blending it in with a whisk (as shown above) or by keeping the pan in constant motion. The action is similar to that used in finishing a sauce with butter (monter au beurre). If the sauce looks oily rather than creamy or if it appears to be separating, it has gotten too hot. Immediately pull the pan off the heat and set it on a cool surface. Continue to add the butter a little at a time, whisking until the mixture regains the proper creamy appearance. Then continue to incorporate the remainder of the butter over low heat. If the butter takes a very long time to become incorporated into the sauce, increase the heat under the pan very slightly.
2. Make the necessary final adjustments to flavor and texture by checking the seasoning and straining, if desired. Alternatively, the reduction ingredients can also be left in the sauce for texture and garnish. If you did not strain the reduction earlier, you now have the option of straining the sauce. If you do choose to strain, work quickly to keep the sauce warm. Serve immediately or keep warm. To prepare a large batch of beurre blanc and hold it through a service period, use the same holding techniques described for hollandaise. The sauce may deteriorate over time, however, and must be monitored for quality. The flavor of beurre blanc is that of whole butter with piquant accents from the reduction. The finishing and/or garnishing ingredients also influence the flavor. A good beurre blanc is creamy in color, although garnishes may change the color. The sauce should have a distinct sheen. The body should be light. If the sauce is too thin, it probably does not contain enough butter. Conversely, a beurre blanc that is too thick includes too much butter or cream. The texture should be frothy, and the sauce should not leave an oily or greasy feeling in the mouth.