Step 1

If you haven't already, prepare the roasted salsa and corn (and corn tortillas, if needed). At the same time, you can roast the garlic and onion (though many add them to the birria tacos raw).

Step 2

Rehydrate the dried chilies. To do so, place it in hot water (or vegetable stock) for about 30 minutes (the time will vary based on the size of the chili). You can use any leftover soaking liquid to add to stocks and soups.

Step 3

After the chiles have rehydrated, remove the stems, and use a sharp knife to scoop out the seeds. Then add the chiles and all remaining birria marinade ingredients to a small blender or food processor and blend.

Step 4

Meanwhile, clean the mushrooms if needed (I use kitchen paper towels to gently rub away any dirt), then slice them into thin strips.

Step 5

Combine the chopped mushrooms and marinade in a bowl well and toss to thoroughly coat.

Step 6

Spread the marinated mushrooms over a parchment-lined baking tray and bake in the oven for around 20 minutes at 400ºF/200ºC.If you'd like the birria mushrooms to be crispier, you can broil them for a few minutes at the end of the baking process. However, I prefer mine to be a little "juicier," so I skipped that step.

Step 7

Assemble the tacos. I recommend spreading the various toppings out across a large platter so your family/guests can choose their toppings.

Step 8

I like to scoop some mushrooms into the tortillas first, then add the corn and avocado slices before topping with the various garnishes (onions, jalapeno slices, cilantro, and finally a dollop of salsa and squeeze of fresh lime juice).

Step 9

Make ahead: you can prepare various elements for these oyster mushroom tacos in advance. This includes the corn tortillas, salsa, roasted corn, and even the roasted mushroom birria (all of which can be prepared 2-3 days in advance).Store: once baked, any leftover mushroom birria can be stored in an airtight container in the fridge for 4-5 days. The prepared vegan birria tacos are best eaten immediately while fresh to avoid them becoming soggy.Freeze: if you make a large batch, allow the mushroom birria to cool, then transfer to an airtight container and freeze for up to 3 months. Allow to thaw in the fridge overnight before reheating.Reheat: you can reheat the birria on the stovetop for 5-10 minutes. Add an extra splash of water or stock if needed.