Start by soaking your Guajillo chiles in the hot water in a bowl and cover the bowl with a plastic wrap so it softens up. Once the peppers are softened, they’re ready to use. Usually, this takes around 15 minutes.
In a blender add all the marinade ingredients. Add to them the soaked and ready Guajillo chiles. Blend until smooth and silky. Coat the meat with the blender sauce and marinade. You can marinate the meat for as little as 10 minutes or up to 12 hours.
Sauté the onions with the oil. You can use an instant pot or large stovetop pan. Once the onions are translucent, add in the meat and sauce/marinade mixture all at once. Add to that the whole spices. Then add in the stock and cook the stew.
Select pressure high and cook for 40 minutes.
Cover the pot and cook for 1 hour and a half.
Note: The USDA recommends that lamb reach an internal temperature of at least 145 degrees F with a 3-minute rest.
Place all ingredients with onions in an oven safe dish and cover the dish with foil. Roast in the oven at 400 degree F for 1 hour and half. The stew is ready when the meat comes out tender. Preserve the sauce and set aside. Take the meat and use a fork to shred it into fine shreds on a wooden board. Add the meat to bowl along with 3 ladles of the reserved sauce to flavor up the meat.
Dip each tortilla into the reserved sauce to flavor it up. Make sure to quickly dip and remove the tortilla. (This will prevent it from becoming soggy). In a heavy duty pan, place the coated tortilla in the pan and add cheese over half of the tortilla. Pile up the meat over the cheese. Fold over the tortilla to cover the meat and press it down. Flip the tacos when ready and golden and allow it to sear on both sides a total of 5 minutes. Sprinkle the tacos with cilantro and Jalapeños.
Take 2 cups of the reserved birria stew sauce and add to it the onions and remainning cilantro.