11. Place the beef chuck roast in a large pot with 100g of white onion, 15g of garlic cloves, bay leaves, black peppercorns, and 5g of salt. Cover with water and bring to a boil, then reduce heat and simmer for 2 to 3 hours, or until the beef chuck roast is very tender and easily shredded.
22. While the beef chuck roast is cooking, prepare the chiles. Remove stems and seeds from the ancho chiles and guajillo chiles. Place them in a bowl and cover with hot water. Let them rehydrate for about 20 minutes until soft.