Prepare the cooking sauce. Place the dried chiles in a bowl and cover with hot water (I weighted them down with another bowl to keep them submerged. Let sit 10 minutes to soften. Drain the chiles, stem and seed them, then tear into large chunks and put the pieces into a blender. Add the rest of the sauce ingredients up through the water and blend until smooth.
Cook the beef. Season beef with salt and pepper. Working in batches, brown meat briefly in Instant Pot set on sauté, about 3 minutes per batch (you're not trying to sear the meat, just lightly brown so it's not red). Transfer each browned batch to a large bowl. Drizzle in additional oil as needed between batches.
Return all the beef to the Instant Pot, along with any accumulated juices. Pour the puréed sauce through a medium-mesh strainer over the meat. Pour the beer over the meat and stir to combine everything. Lay the avocado leaves on top of the meat. Seal the Instant Pot and cook on high pressure for 1 hour.
When the pot shuts off at the end of the timed cooking, let it sit undisturbed for 10 minutes. Then, wearing an oven mitt, turn the steam release handle to open. When the float valve drops down, you can safely open the pot.
Assemble the tacos. Warm the tortillas—while they are traditionally heated on a griddle or in a dry pan, we prefer to microwave them, to keep them pliable. Cut or shred enough of the beef chunks for your tacos. Put a generous amount beef on each tortilla and drizzle with a little of the sauce from the pot. Top with cilantro, onion and hot sauce, if desired. You can also customize with other taco toppings you like—avocado, sour cream, shredded cheese... Serve.