Place the chilies, onion and garlic on top of the griddle and toast. Toasting the chiles makes them spell some oil that changes the taste and makes them more delicious but you need to be fast! just toast the chiles for 3 to 5 seconds per side.
As soon the chilies start smelling take them out of the griddle. If they burn out you will need to get rid of them and start over with new chilis. Do not use the burned chiles as they can give the recipe a bitter flavor.
Have some hot water ready, and submerge the chilies in it for about 5 minutes so they can rehydrate.
In the blender add the ingredients that we just toasted along with 1 tablespoon oregano, ½ teaspoon cumin, 1 tablespoon salt, 5 black peppercorns, and 3 bay leaves.
Add 1 cup water and bled all together until liquified. Pass through a sieve and save the sauce.
Pour the sauce on top of the beef/meat and you have two options, let it marinate overnight or just a couple hours. I have made both and they turn out delicious as either way.
Instant Pot: Use the Meat/Beef option.
Slow Cooker barbacoa street tacos: 8 hours in low temperature or 4 hours in high temperature
Oven: Cover an oven-safe container with foil paper and cook at 360f for about 4 hours or until the beef is ready.