In a large stock pot (that can handle at least 4 L), over medium high heat, sear the quartered white onion, 5 garlic cloves, and 2 medium quartered tomatoes. Some parts will get blackened a bit, that's the goal.
Lower the heat down to medium, then add water, 24 dried shiitake mushrooms, 6 tbsp apple cider vinegar.
In a tea bag/tea strainer/fine mesh bag, add in peeled ginger (I slice into coins), 1 tsp each coriander seed and black peppercorns, 4 cloves, and two dried bay leaves. Bring the broth to a boil then lower to a simmer and cover to cook for at least 30 minutes until the mushrooms have fully softened.
Meanwhile, the chiles should be done boiling and may have cooled enough to go into the blender. In a high powered blender (like a Vitamix or Blendtec), combine the chiles and the boiled chile water, and everything from the pot EXCEPT the mushrooms, the spices from the broth in the tea strainer/tea bag, 3 cubes of vegan beef-style bouillon cubes, 2 tbsp mushroom broth powder, and 1/8 tsp MSG.
Blend until completely pureed and then add back to the pot. If your blender isn't powerful enough, pour through a fine mesh strainer and then discard what you can't blend.
I also add the mushrooms back into the pot, plus 1 lump of rock sugar and cover to keep everything simmering for at least another hour, ideally 2 hours.
Remove mushrooms and gently squeeze out the liquid from the mushrooms. You can thinly slice these to add to your quesabirria tacos but I usually just snack on them because I live with mushroom haters.
Taste for seasoning (add more salt if necessary), and then set aside.