In a Dutch oven, add in garlic, pork loins and onion. Fill with water, enough to cover ingredients. Bring contents to a boil. Once boiling, reduce heat to low and simmer for 2 hours.
Remove seeds and stems from chile pods. Place chiles into a saucepan, pour in 2 cups water and simmer, uncovered, for 20 minutes. Pour chiles and water into a blender. Puree until smooth. Strain the mixture. Add 1 1/2 teaspoons salt to chile mix.
Shred the pork, add in 1 cup of chile mix. Toss together.
Place cornhusks in a bowl of warm water and let soak. Remove from water and pat dry once well soaked.
In a separate bowl, beat together a tablespoon of beef broth with lard. Beat until fluffy. Add in remaining salt, masa harina and baking powder. Beat together, add more broth to make spongy dough.
Spread a thin layer of the dough into the cornhusks, about 1/4 inch thick. Add a tablespoon of pork into the middle and fold sides inward. Steam for 1 hour.
Remove husks from tamales, drizzle the remaining sauce over each tamale. Top with sour cream.