Soak the dried corn husks in warm water for at least 30 minutes to soften. Drain and pat dry before using.
In a medium saucepan, bring 3 cups of chicken broth to a boil.
Add the quartered onion, garlic cloves, dried guajillo and ancho chiles to the boiling broth. Reduce heat and simmer for 15 minutes until chiles are softened.
Remove the chiles, onion, and garlic from the broth and transfer them to a blender. Add cumin, oregano, and black pepper. Blend until smooth to create the red chile sauce.
Strain the sauce through a fine mesh sieve back into the saucepan. Simmer on low for 10 minutes. Season with salt to taste and set aside.
In a large mixing bowl, combine masa harina, baking powder, and salt.
Add the softened lard or vegetable shortening to the masa mixture. Using your hands or a mixer, beat until the mixture is light and fluffy, about 5 minutes.
Gradually add 2 cups of the reserved chicken broth (from step 2) to the masa mixture, mixing well until the dough is soft but not sticky. Add more broth if necessary.
Stir half of the red chile sauce into the shredded chicken until evenly coated.
To assemble each tamale, spread about 2 tablespoons of masa dough evenly over the smooth side of a soaked corn husk, leaving a 1-inch border on all sides.
Place 2 tablespoons of the sauced shredded chicken in the center of the masa.
Fold the sides of the husk in toward the center, then fold the bottom up and the top down to enclose the filling.
Repeat with remaining husks, masa, and chicken filling.
Place a steamer basket in a large pot filled with 2 inches of water. Bring water to a boil.
Arrange tamales upright in the steamer basket with open ends up. Cover the tamales with a damp kitchen towel and then cover the pot with a lid.
Steam tamales for 1 hour to 1 hour 15 minutes, adding water as needed to prevent drying out. Check doneness by peeling back a husk; the masa should be firm and separate easily from the husk.
Remove tamales from the steamer and let cool for 10 minutes before serving.