For the tamales, cover the meat with water in a saucepan, add 2 cloves of garlic, as well as the onion, put a lid on and cook the meat until tender, about 45 minutes. Drain, reserving the clear soup. Cut the meat into thin strips and set aside.
Steep the chilies in 500 ml of hot water for 10 minutes, then puree with the remaining 2 cloves of garlic. Heat the puree in hot lard for 3 minutes, stirring. Add the meat, season with salt, cook for another 3 minutes until the sauce thickens.
Mix the cornmeal with 250 ml of the beef broth in a baking bowl good and let stand for 10 minutes. In a second bowl, whip the lard until creamy, then add it to the cornmeal along with the baking powder and salt and mix well.
Put 1 tablespoon of the mixture on each corn leaf and a little of the meat filling on top. Fold the edges of the leaves toward the center – the filling should be covered. Fold the ends over this to make compact packets – the tamales.
In a large steamer pot, fill water. Spread the steamer insert with corn leaves. Place the tamales upright along the edge and steam for 1 hour with the lid closed. To test, open one tamal: The filling should release easily from the wrapper.
Arrange the tamales and serve.