Place pork into the oven with onion and garlic and pour water to cover. Bring it to boil, then decrease the heat to low and bubble until the meat is cooked thoroughly, about 2 hours.
Put chiles in a saucepan with 2 cups of water. Use rubber gloves to detach seeds and stems from the chile pods. Simmer, lay bare for about 20 minutes, then take off from heat to cool. Bring the chiles and water to a blender and blend till smooth. Strain the mixture, mix some salt, and put it aside. Shred the cooked meat and combine with one cup of the chile sauce.
Soak the corn husks in a bowl of lukewarm water for 20 minutes or until softened. In a large pan, beat the lard with a tablespoon of the broth until fluffy and smooth. Mix the masa harina, baking powder, and salt; blend into the lard mixture, adding more broth to form a pulpy dough.
Disperse the dough over the corn husks to 1/4 to 1/2 inch thickness. Put one tablespoon of the meat filling in the middle. Turn over the sides of the husks toward the middle and place them in a steamer. Steam for 1 hour.
Separate tamales from husks and sprinkle remaining chile sauce over. Top with sour cream. For a creamy sauce, blend sour cream into the chile sauce.
To test if the tamales are done, remove one tamale and manage to pull the husk off. If the husk pulls away neatly from the tamale, they’re done. If the dough is still damp or sticky, let them be cooked for 8-10 minutes longer and try again.
Store the leftover tamales in the refrigerator for about a week, depending on the freshness of your ingredients.
