Heat a large skillet over medium heat. Add 1 1/2 tablespoons of the vegan butter or olive oil. Once melted or hot, add the diced shallots with a pinch of kosher salt. Sauté until translucent and golden, about 3 minutes.
Add the remaining 1 1/2 tablespoons butter or oil and the mushrooms. Increase the heat to medium-high and cook for 8-10 minutes, stirring only occasionally so they get some color, until the mushrooms release their liquid and are nicely browned.
While mushrooms are cooking, whisk together the nutritional yeast, cornstarch and plant-based milk.
Add the minced garlic, thyme, rosemary and season with 1/4 teaspoon kosher salt and several cracks of black pepper. Cook for 1 to 2 minutes, stirring frequently, or until very fragrant.
Add the red wine, vegetable broth, and soy sauce and bring to a boil. Whisk frequently and allow to boil for 3 to 4 minutes to cook off the wine. Add the nutritional yeast roux to the pan, whisking constantly to make sure it dissolves and thickens, about 2 minutes. Then add in the miso paste and stir well to incorporate it into the gravy. Adjust the heat to maintain a simmer and cook for 3 to 4 minutes, whisking very frequently, until the flavors have melded together.
If you want a smoother and creamier consistency, scoop out 1 cup of gravy (about 2 ladles) into a blender or food processor. Blend until smooth. Add the blended gravy back to the pan and mix together.
Add the vinegar, stir to combine, and taste. Add salt or pepper to taste. Finish with chopped parsley, if using.