Summarize the following:
Adding salt to beaten eggs starts breaking down the proteins, releasing moisture and creating a less uniform consistency in the egg mixture. This means that the eggs will temper less evenly when you add broth. Season the broth after the eggs have been tempered and added into the soup, not before you temper the eggs. Ladle out some of the broth, spooning in a small amount to the bowl with the eggs in it. Whisk the eggs vigorously while you add the liquid. Count to ten before you add another spoonful and allow the temperature to come up gradually. Try as best you can to only use broth to temper the eggs. Depending on what kind of soup you're making, it can be hard to avoid little chunks of vegetables or meat. It's fine if you get a bit of veg in there with your eggs–it's all going together anyway–but the eggs will whisk easier with just broth and egg, and the eggs will temper more quickly. Continue adding broth in small amounts and put your hand on the side of the bowl to check for the temperature. Look closely for steam. If you're doing it properly, the eggs should still be perfectly liquid, but should be steaming and warm, meaning that they're tempered properly. When you see steam, your eggs are tempered. When the bowl is steaming as much as the pot with the broth, you can pour the tempered eggs directly into the soup. Stir the eggs around to enrich the broth with the tempered eggs. The broth should thicken some–not much–and will take on a cloudier, slightly yellowish or milky color.
Don’t season the eggs. Start with a very small amount of broth. Continue adding until the bowl is steaming. Pour the mixture back into the soup pot.