Hollandaise, Béarnaise, and their derivatives make up a class of emulsion sauces that also includes the cold sauce mayonnaise. These sauces are prepared by emulsifying melted butter or oil into egg yolks, through rapidly whisking the ingredients, to break the butter or oil into tiny droplets that are held in suspension by lecithin in the yolks.
These sauces usually include wine, wine vinegar, or lemon, sometimes as cooked reductions, which denature the yolks and help to stabilize the sauce. The acids also raise the coagulation point of the yolks to about 190°F/88˚C to help prevent curdling.
Emulsion sauces are sensitive to heat and cold and must be held at a temperature of 120-130°F/50-55˚C. Use an insulated thermos for best results. Because this sauce must be held in the danger zone, the recommendation is to prepare it as close to service as possible and discard it after 2 hours.
Rescuing a Broken Emulsion – Don’t Throw it Out!
If an emulsion breaks either in preparation or as it sits all is not lost – don’t throw it out! To rescue a broken sauce start with a clean bowl and add one per two yolks along with 1 Tb. water per yolks. Whisk in a hot water bath until it begins to thicken. Remove from the heat and using the same initial setup, add the broken sauce into the fresh cooked egg yolks. The sauce may become thick so more water may be needed to adjust consistency. More butter may also be needed to adjust the ratio of egg to butter.
Beurre Blanc Sauce
Beurre blanc sauce is a warm butter emulsion that is prepared with a reduction of wine, wine vinegar and shallots. Reduced cream is sometimes added to the reduction as a stabilizer. Diced butter is whisked into the sauce over low heat until it is emulsified into the sauce. Like hollandaise and béarnaise sauce it is fragile and cannot be held in a steam table. Hold in a thermos at 120°F/50˚C.
Beurre monté refers to melted butter that remains emulsified, even at temperatures higher than that at which butter usually breaks down. Beurre monté may refer either to the melted butter sauce itself, or to the method of making it.
Butter is an emulsion of about 2% milk solids, 80% milk fats (clarified butter), and about 18% water. At 160˚F/71˚C, butter normally breaks down into separate components parts, but in a beurre monté, the butter is heated in such a way that it holds an emulsion up to 180-190˚F/ 82-88˚C. It is versatile as a sauce, as an ingredient for other sauces, as a poaching medium, or as a resting medium for cooked meats.
In order to make a beurre monté, boil a very small quantity of water, 1-2 oz. /30-60 ml; once the water has come to a boil, turn the heat down and start whisking the cold butter into the water, one or two chunks at a time. Add more butter whenever the chunks have melted. Once the emulsion is started, more butter can be added at a time. Continue adding butter while whisking until one has the desired quantity of beurre monté. To avoid breaking the sauce, the beurre monté must then be held warm, but below 190°F/88˚C.