Before you dump out that pan of beef broth, think of all the ways you could be using it. You can add flavor to vegetables by cooking them in the broth or use it as a base for a soup. Even better, you can make a brown gravy to top your mashed potatoes or steak. But to use it as a gravy, you will first need to thicken the broth. The two most common ways to thicken broth are to make a roux or a slurry.
Melt 1/2 cup butter in a saucepan over medium heat.
Stir in 1/2 cup flour. There should be no lumps after the butter and flour have been combined into a roux. Allow the mixture to brown.
Adjust the heat to low. Slowly begin pouring 4 cups beef broth into the saucepan as you whisk the roux and broth together.
Turn the heat to medium after all of the broth has been mixed with the roux. Bring the gravy to a boil.
Put 2 tbsp. flour and 1 cup warm beef broth into a jar.
Place the lid on the jar and begin shaking it. Shake the mixture until the flour has dissolved into the broth. This is mixture is called a slurry.
Pour the slurry into to a saucepan filled with 2 cups warm beef broth. Stir the mixture the entire time you are combining the slurry and broth.
Adjust the heat to medium-high and let cook for a couple of minutes. The broth will thicken into a gravy.