Prepare the husks: simmer the husks in water to cover for 10 minutes, weighting them with a plate to keep them submerged, let stand for a few hours until they are pliable To make dough: Beat the lard in a mixer until very light, for about 1 minute Add 1 cup masa to lard, beat until well blended.
Continue beating adding alternately the remaining masa and the poultry broth only adding enough broth to give the consistency of a medium thick cake batter.
Sprinkle the baking powder and salt.
Beat 1 minute more.
To make the salsa: Husk and wash the tomatillos.
Put the tomatillos and serrano chiles and some salt in a pot of water and boil them until tender, about 10-15 minutes.
Drain and put them into the bowl of a food processor.
Add the coriander, onion and garlic.
Process until smooth.
Heat 1 Tbsp of the lard in a medium large skillet over medium high heat, when the lard is hot enough to make a drop of the tomatillo puree sizzle, pour it all in at once.
Stir the sauce constantly for 45 minutes until it gets darker and thicker, thick enough to coat a spoon.
Add the chopped tomatillos and cilantro.
Season with salt.
Mix the shredded chicken with 1/2 cup of the cooked tomatillo sauce.
To form the tamales: Remove the husks from the water when they have softened Pat husks dry.
Tear the extra husks into 1/4"x7" long strips for each tamale.
Take a husk that is at least 6"x7", lay out with tapering end toward you.
Spread a couple of Tbsp of dough mixture into a square, leaving at least 1-1/2" border on side towards you and a 3/4" border along other sides.
Pick up 2 long sides of corn husk and bring together, overlapping one over the other.
Fold up the bottom section of husk tightly right up to the filling line.
Leave top open.
Secure it in place by loosely tying one of the strips of husk around the tamale.
Repeat with remaining husks and dough mixture.
Stand the tamales on the folded bottom in a prepared steamer, being sure they are not packed too closely so they can expand.
Cover with a layer of leftover husks.
Cover with lid and steam for 1 hour.
Check carefully that all the water doesn't boil away, adding boiling water when necessary.