Soak the Dried Corn Husks in hot water for 30–45 minutes until pliable; drain and set aside standing upright so excess water can drip out.
Make the pork: in a large pot combine the Pork Shoulder with a halved White Onion, several smashed Garlic Clove, a Bay Leaf, a generous pinch of Salt and enough Water to cover. Bring to a simmer, skim foam, then cook gently until the meat is very tender, about 1½–2 hours.
When the pork is done, remove it and reserve about 3 cups of the cooking liquid as your Pork Cooking Broth; shred the pork with two forks and discard the bay leaf and large onion pieces.
Prepare the chiles: stem and seed the Dried Guajillo Chile and the Dried Ancho Chile. Toast them briefly in a dry skillet until fragrant, then soak in hot water or some of the warm Pork Cooking Broth for 15–20 minutes until soft. Drain, reserving the soaking liquid.
Make the chile sauce by blending the softened chiles with the toasted soaking liquid or a splash of Pork Cooking Broth, a small chunk of the cooked White Onion (or raw if you prefer a brighter note), another peeled Garlic Clove, a teaspoon of toasted Cumin Seeds, a pinch of Mexican Oregano, a little Salt to taste and a tablespoon of Apple Cider Vinegar. Blend until very smooth, then simmer the sauce in a saucepan for 8–10 minutes to deepen the flavor and thicken slightly.
Combine the shredded pork with enough chile sauce to coat it evenly; taste and adjust seasoning with more Salt or a splash of Apple Cider Vinegar if needed.
Prepare the masa: in a large bowl mix the Masa Harina with Baking Powder and a pinch of Salt. Add softened Lard and pour in warm Pork Cooking Broth a little at a time, mixing and then beating the dough (with a stand mixer or by hand) until light and fluffy and it holds together—spreadable but not runny.
Assemble the tamales: lay a softened Dried Corn Husk flat, spread about 2–3 tablespoons of masa into a thin rectangle in the center, then place a spoonful of the pork filling on top. Fold the sides of the husk over the filling, then fold up the bottom to enclose. Repeat until all masa and filling are used.
Steam the tamales upright in a large steamer basket over simmering water (cover the top with a layer of leftover husks or a clean towel to keep steam in). Steam for 1 to 1¼ hours, checking water level occasionally—tamales are done when the masa easily separates from the husk.
Let the tamales rest 10–15 minutes after steaming, then serve warm straight from the husk with extra chile sauce on the side.
