Hollandaise is famous because it's tasty, it's fattening, and it's supposedly difficult to make. The first two points are true but the last one is not. British home cook Nigella Lawson refers to Hollandaise as "a kind of hot mayonnaise" because it's composed primarily of eggs and butter, with a little lemon juice or white vinegar, and pepper for vital flavoring. The difficulty lies in cooking it so it's neither runny nor curdled. If it's runny, it means the eggs were not cooked sufficiently. If it's curdled it means you don't have a nearly pudding-like emulsion because the butter has separated from the other ingredients.
Making it properly is simplicity in itself, but it takes practice. First, I recommend dispensing with the double boiler most recipes demand. You don't need it. Secondly, I find using lemon juice and white vinegar together gives the sauce a piquant vibrancy, without being too lemony or too sour. Since that is a matter of taste, though, you will want to experiment.
2 egg yolks
pinch of cayenne pepper
salt and white pepper
2 teaspoons lemon juice
2 teaspoons white vinegar
4 ounces (1 stick) butter, cut into half-inch pieces
Turn an electric burner onto medium-low, or gas onto low, and drop the egg yolks* into a small saucepan** along with the lemon juice and vinegar, cayenne pepper, salt and white pepper. Immediately start whisking the eggs. It should take two or three minutes of careful attention before they start to cook. As soon as the eggs start to thicken, turn the burner down one notch, otherwise they are likely to turn into scrambled eggs. If they start to solidify instead of thicken it means the heat was too high and you will just have to start over. If they don't thicken it means the heat isn't high enough, so turn up your burner a notch.
As soon as the eggs start to thicken, begin adding the butter a little at a time, whisking continuously. If the sauce starts to thin out, it means you're adding the butter too fast; either your butter chunks are too big or you're adding them too quickly. Either way it means too much butter at once, so adjust. After about five minutes of whisking, you should have a nice pudding-like Hollandaise. This is a good time to taste it, then adjust the seasonings. I find a nice fat pinch of cayenne is perfect, along with small pinches (or a couple of shakes) of salt and pepper. It's best to use white pepper, because then you don't have black specks in your sauce. As soon as the sauce is complete, take it off the burner. If you leave it on the heat it will almost certainly overheat and curdle. It will cool rapidly off the heat and thereby maintain it's consistency. It's best used as soon as possible, however.
Leftover Hollandaise can be successfully frozen, something nice to know since it's touchy and a bit time-consuming to make. It's also economical and convenient for a small household to make up a batch, knowing there will be some left for another meal. Heat frozen Hollandaise slowly on a very low burner, whisking or stirring constantly. Alternately, it will heat up nicely in the microwave. Again, a low setting is the key. Try the defrost setting for one to two minutes. If it's still partially frozen, then stir it and try heating for an additional 30 seconds at a time on an even lower setting, followed by a quick stir each time, until it reaches the proper consistency.
This is wonderful over asparagus, broccoli or salmon.