Hollandaise and Béarnaise sauces are emulsions of melted butter and egg yolks. They begin with reductions of wine, wine vinegar, peppercorns, and in the case of Béarnaise sauce the addition of shallots and tarragon. Acids (wine, wine vinegar, or lemon) are added to balance the richness of the butter, and help prevent the yolks from curdling by raising their coagulation point. These sauces should be held at low temperatures, 120°F/50˚C. Because they contain egg yolks and must be held in the food temperature danger zone, prepare as close to service as possible and never hold for longer than 4 hours before discarding.
