When You Don't Have Time To Make A Roux, A Simple Egg Yolk Will Do
A roux is a simple mixture of butter and flour combined in a ratio of one to one that's used to thicken sauces, soups, and gravies. Preparing this thickener is easy, but when you're in a hurry, it can feel like a time-consuming chore: From weighing the butter and flour and whisking them in a pan into a smooth paste to ensuring it cooks through without darkening too much, there are obviously many moving parts to this basic preparation. Luckily, there's a quicker solution: an egg yolk.
Using egg yolks to thicken sauces and soups may not be common, but this one-ingredient thickener works wonderfully to create a smooth and rich texture. Your soup won't just get thicker, it'll acquire a delicate creamy appearance without using cream or flour. Furthermore, egg adds a luscious richness that instantly elevates the flavor of the dish. And if you're gluten intolerant or cooking for someone who is, egg yolks will make the ideal thickener by eliminating the need for flour.
Additionally, keep in mind that egg yolk is an emulsifier. This means that any soup or sauce containing both water and oil can be bound by the water and oil components in the yolks. A great example is how egg yolks create a creamy salad dressing resulting in a homogenous sauce. This is something you won't get from a roux.
How to use egg yolks to thicken soup
Using egg yolks as a thickener is a simple process, however, you must be mindful of the temperature. Don't use too much heat lest the yolks scramble but also don't use too little heat and risk serving raw eggs which could end up being a food safety issue. Aim for the middle ground by tempering the yolks before adding to the entire pot of soup.
To do this, begin by cracking the eggs and separating the yolks into a bowl. As a starting point, use four egg yolks for every 6 cups of soup. Beat the yolks until they turn into a smooth consistency. Now it's time for the tempering process. With the pot of soup simmering at a very low temperature, you'll need just a little to add to the yolk. Take one spoonful of the soup at a time and slowly add to the yolks while continuing to whisk the yolks vigorously.
This process will gradually raise the temperature of the egg yolks hence preventing them from scrambling. Once the yolk mixture reaches about 160 degrees Fahrenheit, you can now transfer it back to the pot of soup. Keep stirring at low heat and you'll soon notice the entire soup starts to thicken. Alternatively, instead of separating the egg yolks, you can use whole eggs and follow the same process to thicken the soup. It works just like with a Greek avgolemono soup.