Rehydrate the dried chiles in hot water for 30 minutes.
For the stew, heat oil in a medium pan over medium heat. Add onions and cook until translucent, so about 4-5 minutes. Add garlic and continue to stir for a couple minutes. Add all the ground spices and salt. Gently stir with the onions and garlic for a minute.
Add crushed tomatoes, chipotle peppers, and adobo sauce. Let the sauce reduce for a few minutes before finising with vegetable broth and apple cider vinegar. Simmer for 10 minutes. Let it cool down a little before blending with the rehydrated chiles.
Shred the oyster mushrooms by hand. You can do this while the stew simmers and cools down.
After blending the stew, pour it back into the pan and gently simmer with 2 bay leaves.
In another medium pan, heat 1 tbsp oil over medium heat. Lightly fry the shredded mushrooms until crisp and golden on both sides, so about 8-10 minutes. Pour 1¼ cups of the stew on the mushrooms, which should be just enough to fully coat them. Stir for a few minutes.
To make a birria taco, coat each side of the tortilla in the leftover stew, so it is covered with it but not soggy. Fry the tortilla in a teaspoon or so of oil in a nonstick over medium heat for about a minute. Flip and pile on 1.5 tbsp of filling on one side. Sprinkle some vegan cheese. Close and cook on both sides until crisp.
Garnish with cilantro and onion. Finish with a squeeze of lime!