Traditional tamales are wrapped in corn husks or banana leaves, but you may also use parchment paper. Butter is substituted for the traditional lard in this recipe too.
Soak the corn husks in warm water for 2 hours to soften.
Mix the masa harina with the hot water and set aside. Whip the butter with the baking powder in a stand mixer with the paddle attachment until it is fluffy. Add the masa harina 1 cup at a time, beating it into the butter. Beat in the chicken broth and beat for 1 more minute. Beat in the salt and additional broth if necessary to achieve the consistency of fluffy muffin batter.
Mix the meats with the olive oil, cumin, chili powder, and garlic salt and set aside. Take the cornhusks out of the water and lay them out on a clean kitchen towel to drain. Cover each husk with a ½-inch-thick layer of the masa harina mixture, leaving an L-shaped border of 1 inch on two consecutive sides.
Put 2 tablespoons of meat mixture in the middle of the masa harina mixture on each husk. Roll the tamales closed starting with the side with no border. Fold up the other border end to enclose the roll on one end. Place the finished tamales seam-sides down so they don't unroll while you finish the others.
Place the tamales in a deep steamer or pasta-cooker basket with their open ends up. Pack them next to each other so they stand up straight. Place the basket in a pot over boiling water, cover with the lid, and steam the tamales for about 35 minutes. Add water if necessary so the pot doesn't run dry. Serve the tamales in their husks; they can be peeled off by each diner.