1For the Tamales, mix masa harina and hot water in large bowl; let stand 5 minutes. Place lard, salt, oregano, and baking powder in separate large bowl. Beat with electric mixer on medium speed until light and fluffy, about 2 minutes. Gradually add masa mixture, beating on low speed, until well blended. Gradually stir in chicken stock. Beat 1 minute longer, until mixture sticks together and will hold shape when scooped. Cover and refrigerate 1 hour. Beat dough, adding additional stock as needed, until original consistency before refrigerating is reached.
2Soak corn husks in hot water at least 30 minutes or overnight, until soft and pliable. Drain. Tear two of the corn husks lengthwise into 6 thin strips each to use as ties.
3For the Chicken Filling, remove bay leaves and nutmeg from the Tamale Mixed Spices package; set aside. Remove stem and seeds from chili and tear into pieces.
4Heat large skillet on medium-high heat. Place remaining spices and chili pieces in skillet; toast until golden brown, about 1 minute. Immediately remove from pan and place in a heat-safe bowl. Add boiling water and let stand 10 to 15 minutes until softened. Transfer to blender container. Add tomatoes, onion, garlic and salt; cover. Blend on high until smooth.
5Heat oil in large deep skillet on medium heat. Stir in sauce and bay leaves. Add chicken thighs. Bring to simmer; cover. Cook 40 to 45 minutes until chicken is tender
6Transfer chicken to large bowl. Shred into fine pieces with two forks; discarding skin and bones. Return chicken to sauce in skillet. Cook 10 minutes longer until thickened.
7To assemble each tamale, spread 3 tablespoons masa dough into 4 1/2 x 4-inch rectangle at the wide end of corn husk. Spoon 2 tablespoons of the Chicken Filling over the masa. Grate nutmeg and sprinkle lightly over filling. Bring long sides of husk up to enclose filling with masa. Roll husk around tamale. (Do not roll husk into masa.) Fold up the narrow end of the husk, keeping the top end of the tamale open. Tie tamale with husk strip. Repeat until all masa dough and filling is used.
8Pour about 1 to 2 inches of water into large pot. Bring to boil. Stand tamales, with open ends up, in steamer basket, making sure basket is not touching water. Cover tamales with kitchen towel. Cover pot with lid. Steam on medium heat 1 hour and 15 minutes to 1 hour and 30 minutes, or until husk peels away easily from tamale and masa is slightly firm. (Add additional water to pot as needed to maintain steam.) (Tamales will continue to firm up when removed from heat.)