Place pork and 5 cups of water in a stock pot to cook over medium heat.
Put 6 cloves garlic, 1/4 onion, 1 cup of water and 2 teaspoon salt to a blender; puree until smooth. Add mixture to stock pot and cook uncovered for 20 minutes. Cover, cook for an additional 30 minutes. Strain and reserve the liquid. Return pork to the pot.
In the meantime, soak the chiles for 20 minutes in hot water. Drain when chiles are soft and discard the water. Remove seeds and tops. Put in blender with remaining 1 clove garlic, remaining 1/4 onion, chiles, 3 cups strained pork stock and remaining 1 teaspoon salt; puree until smooth.
Pour sauce mixture over pork. Cook over medium heat, covered for 10 minutes.
Set aside to cool. Refrigerate the filling for a more “manageable” filling because the sauce will be thicker.
After the corn husks are soft, take some of them out of the water, shake the water off and lay them on the counter on a towel.
Spoon masa on the center of a corn husk. With the back of a spoon. Spread 1/8-to-1/4-inch thick. Add a small amount of filling and bring the sides of the corn husks together, folding so that it encloses the filling. Twist the ends of the tamale and secure by tying with small strip of corn husk. Wax paper can be used as an additional wrap.
Place tamales in a steamer or on a rack in a pot deep enough to steam. Add water just below the steamer, cover with a tight fitting lid and steam about 1 hour. Add water as needed to maintain water level. Tamales are ready when masa pulls away from husks. A thin cloth can be used under the lid to make a tighter fit.