Cover pork with 15 cups of water. Add 1 tablespoon of salt and whole head of garlic. Bring to a boil, then lower the heat and cook at a steady simmer for 4 hours, or until pork becomes tender. Skim the foam off from pork as it cooks. Flip pork over halfway through cooking time.
Place the corn husk in a large pot and cover with boiling water. Cover and let soak for a few hours. The longer the better. I soak mine for overnight, changing the water the next day.
Remove the stems and seeds from chile ancho, transfer to a pot and cover with water. Bring to a boil then reduce the heat and cook for another 10 to 12 minutes. Remove from heat and let cool for a few minutes.
Drain the peppers and transfer them to a blender. Add 3 cups of pork broth(from cooking pork), 1 tablespoon oregano, 1 tablespoon of garlic powder, 1/2 tablespoon cumin, 2 teaspoons salt, 2 teaspoons black pepper. Blend in two batches if needed. Blend until smooth, set aside 1 cup to add into the masa dough.
Once the pork is cooked, remove from the broth and let it cool for a little while. When cool enough, shred the pork or chop small. Heat 3-4 tablespoons of manteca or canola oil to medium heat in a large pot. Add the chile ancho sauce from the blender and cook for 5 minutes. Add in all of the pork and 1 1/2 to 2 cups of remaining pork broth. Cook at a low simmer for 40 to 50 minutes or until the broth reduces. Taste for salt.
Prepare the masa dough: Combine masa harina, baking powder and salt in large bowl, gradually add 4 cups warm pork broth. Add 1 cup of reserved chile ancho sauce. Using your hands, work into a soft dough. In another glass bowl, melt the manteca. Add the lard/manteca and remaining 1 cup of warm broth to the masa and work with hands for 7-10 minutes. The masa should have a frosting like texture. If the masa seems too thick, add a little more broth. Always taste the masa for salt. Very important. Keep masa covered with a damp paper towel or plastic until ready to use.
To assemble tamales: Take a few of the husks at a time, shake off water, if they are more than 4 inches wide, just tear off the side a little. Place the corn husk in the palm of your hand with the wide side closest to you. Spread about 3-4 tablespoons of masa all over the bottom half of husk. Place a heaping 2 tablespoons of filling lengthwise down the center of the tamale. Fold one side in first, then the other side (it should overlap a little on the first fold). Fold down the empty top section down and lay tamale seam-side down until ready to cook.
Prepare large pot to steam tamales, Fill the bottom of a large steamer pot with water. Insert the steamer. Arrange all of your tamales standing up (open side up). I like to take a few extra corn husks and arrange them on top of the filled tamales. This will help keep them moist while they steam. Turn heat to high to begin steaming, then reduce to medium for the next 90 minutes. After the 45 minutes, I add a little more hot water to the steamer. Steam for another 45 minutes. Remove from heat and let stand for 30-45 minutes before serving. This will yield 48 medium tamales. Serve with rice, beans and tomatillo salsa!