Soak the dried corn husks in warm water for 30 minutes to soften, then drain and pat dry.
In a medium saucepan, add the guajillo and ancho chilies and cover with water. Bring to a boil, reduce heat, and simmer for 15 minutes until chilies are soft.
Drain the chilies and transfer them to a blender. Add garlic cloves, onion, white vinegar, cumin, oregano, black pepper, and salt. Blend until smooth, adding a little water if necessary to create a smooth sauce.
In a large bowl, combine masa harina, baking powder, and salt. Gradually add chicken broth, mixing until a soft dough forms.
In a separate bowl, beat the softened lard and vegetable oil together until fluffy.
Add the lard mixture to the masa dough and beat well until the dough is light and fluffy, about 5-7 minutes.
Stir the shredded chicken into the chili sauce until well combined.
To assemble each tamale, spread about 3 tablespoons of masa dough evenly over the smooth side of a soaked corn husk, leaving a 1-inch border on all sides.
Place about 2 tablespoons of the chicken filling 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 securely.
Repeat with remaining husks, masa, and filling.
Arrange the tamales upright in a steamer basket with the open ends facing up.
Fill the bottom of a large pot with water, making sure the water does not touch the tamales, and bring to a boil.
Place the steamer basket over the boiling water, cover with a lid, and steam the tamales for 1 hour to 1 hour and 15 minutes, checking occasionally to ensure there is enough water.
The tamales are done when the masa is firm and pulls away easily from the husk.
Remove tamales from the steamer and let cool for 5 minutes before serving.