In a large saucepan set over medium-high heat, melt the butter.
Add the onion and saute for 3-4 minutes, stirring occasionally. Add the mushrooms and saute for 5-8 minutes, stirring occasionally, until the mushrooms are browned and mostly free of liquid. Stir in the garlic, season with salt and pepper to taste, and cook for 30 seconds, until fragrant.
Sprinkle the flour over the vegetables and stir gently for 1 minute. Deglaze the pan with the red wine, using a wooden spoon to scrape up any browned bits that have stuck to the bottom of the pan.
Stir 2 cups of broth and bring the mixture to boil for 3-5 minutes, or until it thickens. Add the thyme, taste, and season with additional salt and pepper if desired. You can also add more broth, up to an additional ½ cup, if you’d like a thinner gravy.
Notes
How to reheat mushroom gravy:
1. Place in a pan over medium heat. Stir frequently and heat until warmed thoroughly.