• Soak the husks: Separate the corn husks and remove any silky threads. Bring 8 cups of water to a boil in a stockpot, remove from heat, and add the husks. Let soak for at least 1 hour.
• Cook the chicken: Add the chicken, garlic, onion, bouillon, and 6 to 8 cups water to a medium saucepan. Water should sit about an inch above the ingredients. Bring to a boil and cook until chicken is cooked through, about 10 to 12 minutes.
• Transfer chicken to a plate. Strain the broth through a fine mesh strainer and reserve.

Make the green chile sauce

• While the chicken cooks, add the tomatillos, onion, garlic, jalapeños, serranos, chicken broth, and salt to a separate pot. Bring to a boil and cook for 10 minutes, until the tomatillos turn yellow.
• Strain the vegetables and transfer to a blender. Add cilantro and cumin. Let cool 10 to 15 minutes, then blend until smooth.
• Pour into a large bowl and reserve ¾ cup of sauce for the masa.

Mix the filling

• Pour the reserved chicken broth into a saucepan and simmer over medium-low for 5 minutes. Set aside.
• Shred the chicken and stir into the bowl of green sauce along with the queso fresco. If the mixture is dry, add warm broth a little at a time. Salt to taste.

Make the masa

• Whip the shortening in a stand mixer until fluffy and smooth, about 5 minutes.
• In a separate bowl, mix the masa flour, baking powder, and salt. Beat into the shortening until incorporated.
• Gradually add chicken broth on low speed until a dough forms. Increase to medium and beat for 10 minutes, until light and fluffy.
• Pour in the reserved ¾ cup green sauce and mix on medium-low for several minutes. Taste and add salt as needed. Cover with a damp paper towel.

Assemble

• Pat a soaked corn husk dry. Place rough side down in your hand or on a flat surface. Spread 2 to 3 tablespoons of masa across the lower half, leaving a small border at the bottom.
• Add 1 to 2 tablespoons of chicken filling down the center.
• Fold the sides of the husk in, then fold the pointy end up like a burrito. Repeat with remaining tamales. Discard any leftover masa.
• Optional: Tie each tamale closed with a thin strip of husk or cooking string.

Steam

• Add water to the bottom of a large pot and set a steamer basket inside. Place a few pieces of soaked husk in the bottom and a ball of foil in the center.
• Stand the tamales open-side up around the foil, working out from the center. Tuck extra husks down the sides.
• Cover and bring to a simmer over medium-high heat. Steam for 1 hour, adding water down the side of the pot every 15 to 20 minutes as needed. Never pour water over the tamales.
• Test by pulling one out and peeling back the husk. If it separates cleanly, they're done. If not, steam another 15 minutes.
• Rest for 15 to 30 minutes before serving.