Make the Birria Sauce (Birria Broth)

1. Prepare your peppers. Remove stems and seeds from peppers and discard. 
2. Boil the chiles, aromatics, and tomatoes. Add the dried chili peppers, onion, garlic, and tomatoes to a large saucepan over medium-high heat. Cover with water and bring to a boil. Once boiling, reduce the heat to a simmer and cook for 15 minutes.
3. Transfer to a blender. Reserve 1 cup of the cooking liquid before straining the rest. Transfer the chiles, onion, garlic, and tomatoes to a high-speed blender. Add the spices (besides the bay leaves), apple cider vinegar, and the reserved 1 cup of cooking liquid. Blend until smooth.
4. Strain and simmer. Strain the blended birria sauce back into the saucepan using a fine mesh sieve. Add the vegan beef broth and bay leaves and simmer for 45 minutes to 1 hour over medium heat.

Prepare the Filling

Note: If you are preparing the birria sauce on the same day as the taco filling, begin to prepare the filling when the sauce has about 15 minutes left to simmer.

1. Sauté the shredded mushrooms. Heat vegetable oil in a large skillet over medium heat. Add half of the mushrooms and cook, stirring occasionally, for 5 minutes, or until the mushrooms lightly brown. Add the remaining mushrooms and cook for another 5 minutes.
2. Add the sauce. Add 1 cup of the birria sauce mixture and cook, stirring occasionally, until the liquid reduces and the mixture becomes jammy, about 8-10 minutes. Add additional salt to taste, as needed.

Assemble the Tacos

1. Prepare the frying pan. Heat a large pan or skillet over medium heat and brush with oil.
2. Dip the tortilla. Dip one corn tortilla into the hearty sauce. Both sides should be coated but not soggy.
3. Add the birria filling. Immediately place the dipped tortilla onto the hot pan. On one side of the tortilla, add the vegan mozzarella cheese and mushroom filling.
4. Cook until crispy. Fold the other half of the tortilla over the filling, press down with the spatula, and cook until crispy and golden brown on each side, for about 2-3 minutes. Remove from the pan.
5. Repeat the process! Repeat the assembly process with the remaining ingredients until all of the tortillas are used if you’ve run out of birria taco filling.
6. Serve. Serve tacos immediately while hot with finely diced onion, freshly chopped cilantro, and a squeeze of fresh lime. Dip in the remaining birria broth and enjoy!