(recipe, Marie Simmons)
Hollandaise is an egg-yolk-thickened, lemony, rich butter sauce unequaled, in my opinion, in the world of sauces. Hollandaise makes Eggs Benedict scrumptious, naps a plate of pristinely cooked asparagus, and cascades regally down the sides of tender poached salmon.
When a hollandaise sauce "breaks" — when the butter and egg yolks are no longer emulsified — it will look curdled. This can happen if the butter is added too quickly or if the sauce is kept over simmering water after you have made it and it gets too hot. In either case, you can "rescue" the sauce (that is, reconstitute the emulsion) by simply removing the pan from the double boiler and whisking in 1 tablespoon cold water. This will lower the temperature of the mixture, stop the curdling, and smooth out the sauce. Set the pan back over hot (never boiling) water and whisk until thickened.