Heat the butter in a large skillet.
Cook the onion and garlic for about 3-4 minutes.
Mix in the flour and let it simmer for one minute.
Mix in the red wine.
To avoid lumps, whisk regularly.
Allow the mixture to simmer for around two minutes (It will thicken.)
Stir in the beef broth.
Let it simmer for 2-3 minutes more until slightly thickened.
Combine the remaining ingredients in a mixing bowl.
Return the mixture to a boil.
Reduce the heat to a low simmer and cook for 15 minutes, covered.
The liquid will begin to reduce.
Salt and pepper to your liking.
Use a strainer to strain the mixture.
Use the au jus immediately or keep it refrigerated until ready to use.