Now, the real fun begins! Pour in the beef broth, Worcestershire sauce, soy sauce, and Dijon mustard. Stir everything together until the mixture is well combined. Bring it to a simmer, and let it cook for about 5-7 minutes, stirring occasionally. The broth will reduce, and the mixture will thicken slightly. This is when the flavors really start to come together, and you’ll notice how much richer it becomes.