In a small skillet, add enough broth to cover the bottom. Add mushrooms, shallot and garlic and cook 5 minutes, or until mushrooms are tender. Add red wine vinegar and cook 2 minutes longer. Remove from heat and set aside.
In a small pot add vegetable broth and liquid aminos (or soy sauce) and whisk in flour and nutritional yeast. Bring to a boil over medium heat. Add in mushroom mixture. Cook a few minutes longer, stirring frequently to prevent clumping, until gravy thickens to desired consistency.
If desired, the gravy can pureed either in a food processor or with an immersion blender.