Start by poaching the chicken breast in a pot filled with salted water for a good 40 minutes at a light boil. After the chicken is cooked, removed from broth onto plate and let cool.
Once chicken has cooled, shred all of the meat and set aside.
In a pot, heat 3 tablespoons of oil to medium heat. Add the onions and garlic. Saute for 5 minutes. Add all of the remaining ingredients listed above for the chicken filling into the pot,, including the shredded chicken.Wait for it to come to a boil, reduce heat, then taste for salt. Add about 1/3 cup of reserved stock. Let it cook down and reduce for a good 30 to 35 minutes. Remove from heat and let it cool.
Combine the masa harina, baking powder, and salt in a large bowl. Add the chicken broth and using your hand, work it into a soft dough. In another bowl, melt the lard or shortening in the microwave. let cool. Add the cooled lard(or shortening) to the masa and work it in with hands until you get a thick frosting consistency. This is where you will add volume to your masa. It does require a bit of mixing to achieve a lighter, fluffier masa. If masa is too thick, add a little more chicken broth. Taste the masa for salt. Keep masa covered with plastic wrap until ready to use. If you have a stand mixer, it will be a lot faster!
Prepare your tamale station. Soak the corn husk in extra hot water for a good 40 to 60 minutes. The longer they soak, the better. Place a heavy dish or pot to keep them submerged in water.
Take a few of the husks, shake off excess water. Tear the husk so they are only about 4 inches wide. Place the corn husk lengthwise in the palm of your hand with wide side closest to you. Spread about 2 to 3 tablespoons of masa all over the bottom half of husk. Place 2 tablespoons of filling down the center of masa. Fold one side in, then the other so they are slightly overlapping. Fold the top flap down and lay the tamale seam-side down
Depending on how big you prepare your tamales, the quantity will vary. I typically make 24 tamales with this masa recipe.
Prepare large steamer pot and fill with water, at least 2 to 3 inches deep. Place tamales open side up around the the edges of pot. Cover tamales with extra corn husk. Cover tightly and turn heat to high to get a quick boil going. Once it begins to steam rapidly, reduce heat to medium. Set timer for 45 minutes.
Keep a tea kettle or saucepan with warm water on a separate burner. After 45 minutes, remove lid from pot and pour in 1 cup of hot water to one side of the pot, careful not to wet the tops of the tamales.
Cover and continue steaming for another 45 minutes. Remove from heat and let tamales sit for 30 minutes to 45 minutes before serving. They will firm up as they cool.