As well as emulsifying, egg yolk thickens when heated. Think custards. By gently heating an emulsion sauce whilst beating, it's possible to create something rich like a mayo and stable like a custard. Neither of these qualities in itself is enough to explain the regal sublimity of the hollandaise, a sauce which outranks the kingly mayonnaise simply by being made with melted clarified butter rather than any healthy vegetable oils.
|250g||clarified unsalted butter|
Watch how to make the hollandaise sauce
Cut the butter into small dice, sprinkle on a plate and place in the fridge.
Make a bain-marie with a bowl over a pan of boiling water. Pour in the egg yolks and whisk them, regularly checking the temperature with a probe thermometer until they begin to thicken at 62°C.
At 62°C remove the bowl from the heat and begin whisking in the butter cubes a few at a time. The temperature will drop. As soon as the butter stops melting easily, put the bowl back over the heat and bring it back up to 62°C.
Once all the butter has been absorbed, whisk in lemon juice to taste, salt and a little black pepper.