Place pork into a large pot with 2 halved onions, 6 bay leaves, 3 garlic cloves, and add water to cover. Boil, and then simmer until the meat is cooked through, about 1.5-2 hours. Remove stems and seeds from the Guajillo or California chili pods (1 bag depending on which chilis you prefer). Place chiles in a saucepan with 2 cups of water. Simmer, uncovered, for 20 minutes, then remove from heat to cool. Transfer the chiles and water to a blender and blend until smooth. Stir in salt to taste, and set aside. In a fry pan, fry the sauce mixture with the olive oil until incorporated. Shred the cooked meat and mix into the sauce. Stir for a few minutes. Soak the corn husks in a bowl of warm water until they soften. Spread the masa on the corn husks to 1/4 to 1/2 inch thickness. Place a tablespoon of the meat fi lling into the center. Fold in the sides of the husks.
Cooking the Tamales
Using a 24 quart tamale steamer, pour enough water to just below the rack height. Boil. Place a few leaves onto the rack, and stand the tamales inside the pot, leaning against the sides of the pot. Cover and simmer gently, steaming the tamales for about an hour. The tamales are ready when the husks lift easily off of the tamales.