Eggs and cream

Egg yolks in particular are used as a thickening base of many of the emulsion sauces, such as hollandaise. Egg yolks combined with cream and added to sauces are known as ‘liaisons’; these are used to thicken and enrich classic velouté sauces, by being added in the last minute of cooking. Liaisons must be added quickly and while the sauce is off the heat, before being thickened over a low heat. As for custard, it must be stirred constantly until the point where it coats the back of a spoon. The sauce must not boil, or it will curdle, and the sauce will have a scrambled-egg appearance. This thickening method is perhaps the most intimidating for the beginner, and may take a bit of practice. But since today’s velouté sauces are made with a cream reduction, rather than with floury, the sauces tend to be rich enough without the need to add a liaison at the end.