Why It Pays To Add An Egg Yolk To Your White Sauces

When we think of white sauces, we associate them with warmth, supreme consistency, and the lovely creaminess they lend to a dish — be it pasta or casseroles. From the cheesy alfredo to the French mother sauces velouté and béchamel, there is a white sauce for every occasion. 

These sauces have a base liquid and a thickening agent made from flour and fat, commonly known as a roux. This agent provides the much-required density and cohesion to turn the fatty ingredients into that creamy, lovely consistency, according to Bon Appétit.  

As simple as these sauces may seem, a small mistake may ruin the end result. For example, a béchamel sauce can become runny instead of velvety if you pour milk into the roux instead of adding it gradually. Not making enough roux or inappropriate heating will make your white sauce split, says Better Homes and Gardens

If cooked at very high heat, it will cause the sauce to overcook, snatching away its delicate creamy taste. You don't want any of this. What you are looking for is emulsification — when all the ingredients live like a happy family.

It acts as a binder

To avoid the dreaded sauce separation, you may want to use an egg yolk to bind your sauce (via Gobble). Get some of your runny sauce from the container, whisk it with yolk, then transfer it back to your sauce container to avoid curdling, recommends The Pioneer Woman. Be mindful of the heat — a very high flame will negate your careful tempering.

This trick is also recommended by Daniel Skurnick, former executive pastry chef of New York's Le Coucou and Buddakan, who told Food & Wine that he adds an egg to any sauce that yearns for thickness. He suggests that cooks make it a part of the roux and also vouches for the flavor it may add to the dish.

If you're low on eggs, there are several other tricks to thicken sauces. You can try adding more liquid if your sauce splits while cooking. If it is beyond repair, use a mixture of oil and liquid and keep adding it until you see it coming together. If these tricks do not work, put the mixture in a blender and whip it till you get a smooth consistency. Reheat before serving, but be very careful, like we said before.