HOW TO MAKE HOLLANDAISE SAUCE
Hollandaise sauce is very buttery, and you can either use normal or clarified butter for it. The former will give a creamy texture, while the latter will produce a firmer hollandaise, due to the amount of milk solids. You also need egg yolks and an acidic liquid to make the hollandaise sauce. Then, you need to combine these ingredients, along with some other aromatics, into a perfect emulsion. We describe the basic technique of making a hollandaise sauce, but you may also come across other sauces that are based on hollandaise (e.g. bearnaise, mousseline) and can use the same skills and techniques for making them as well.
The tricks for making hollandaise sauce are worth mentioning. Firstly, butter needs to be quite warm although not too hot (around 60-63 C/142-145 F) so the sauce will mix and blend together well. The amount of butter and egg yolk is usually 70 g/2.5 oz butter to 1 egg yolk, and it has to be kept fairly within these ranges in order for these two ingredients to mix well together. One last major component in a hollandaise sauce is a kind of acidic liquid, e.g. vinegar or some lemon or lime juice, which provides flavor, water, and also the special effect it has on egg proteins. The acidic liquid is often reduced for more flavor, but it doesn't have to be reduced - it all depends on the final effect that you want to achieve in your hollandaise.
Four servings of a traditional hollandaise sauce require 2 egg yolks, 150 g/5 oz melted or clarified butter, reduction of acidic liquid like lemon juice or vinegar (or a combination of a few of them) along with some aromatic seasonings (crushed peppercorns, salt). You also need a pot of ligthly simmering water over which you can cook your hollandaise in another pot. When preparing hollandaise, make sure to 1./ have everything in place and ready to use, and 2./ to serve the sauce as soon as it's cooked, because the emulsion will not hold itself smooth forever.
Now for the making of hollandaise. To your reduction of acidic liquid with pepper (strained from peppercorns) add the egg yolks and start to stir them with a whisker over a lightly simmering waterbath until the egg yolks are thick and have reached the desired temperature (slightly above 60 C/142 F). The goal is to reach the state when the egg yolks have increased their volume threefold and become ribonned (if you lift the whisker, the egg yolk should fall down from it in shapes of ribbons). If the temperature is too hot, the egg proteins will start to coagulate, first at the bottom of the pan and at its sides. If that happens, remove the pot from the heat immediately and continue to whisk while making sure to decrease the temperature of the simmering water. Then, resume the cooking until you've reached the ribbon stage. Do not overcook or the emulsion will not work! Remove the egg yolks from the stove.
If you do overcook and some egg yolk protein coagulate you can add some cold water too cool the yolks down, and then strain the coagulated portions of the sauce on a fine sieve. You can also start all over, although it can get a little expensive!
Then, start adding the tempered melted butter (also slightly above 60 C/142 F), and whisk at all times as you add the butter in a thin stream. If the sauce reaches a very high thickness, you can dilute it with a small amount of water.
Sometimes, during this operation, the ingredients will stop melting together and the sauce will start to separate. The first rescue trick is adding some water and whisk until the sauce becomes smooth again. This may not work however, so then you need to make use of another egg yolk that you cook as mentioned above (in a separate bowl) and then you add your broken sauce to it and whisk til it's smooth. Add seasonings, according to your desires or recipes; common add-ons are lemon or lime juice, pepper, salt, herbs, etc. The sauce should now have a creamy and smooth texture and it should be easy to pour. Hollandaise sauce holds for a couple of hours, but make sure to hold its temperature at slightly over 60 C/142 F.