Beat 9 ounces of lard in a large bowl with an electric mixer until creamy. Add salt and beat for a few more minutes. Add masa harina and incorporate well. Gradually add chicken broth, 1/4 cup at a time, until masa has a smooth, dough-like consistency. Test by dropping a small ball of masa into cold water; if it floats, it's ready. Otherwise, beat longer.

Combine tomatillos, ancho chile pepper, mulato chile pepper, garlic, salt, black pepper, and oregano in a blender. Blend until smooth.

Heat 2 ounces of lard in a skillet. Cook the tomatillo sauce for 3 to 5 minutes until thickened. Add shredded chicken and some chicken broth. Simmer for 10 minutes until the filling thickens.

Spread 2 to 3 tablespoons of masa mixture onto each banana leaf, leaving a border (2 inches from the bottom and 1/4 inch at the top). Place 1 tablespoon of chicken filling in the center of the masa. Fold the sides of the leaf together, one over the other. Fold the bottom upwards, tie with string, and repeat with the remaining masa and filling.

Place a steamer insert into a pot. Add water to just beneath the steamer. Bring to a boil. Stand tamales upright (open side up) and steam for 90 to 120 minutes until the masa separates from the leaf.