Heat oven to 300°F and arrange rack in the middle. Place 4 pounds boneless beef chuck roast in a large roasting pan or Dutch oven.

Add remaining filling ingredients and cover baking dish with foil or cover Dutch oven with a lid.

Braise beef in oven until tender and falling apart, about 3-4 hours. Remove, uncover and let sit until cool enough to handle.

Remove beef to a large plate. Strain cooking liquid through a fine mesh sieve into a large bowl, reserving solids. Discard any thyme sprigs, cinnamon stick, and bay leaves.

Shred beef into bite-sized pieces. Add vegetables from the braising liquid to the beef and mix to combine. Save the cooking liquid for the masa.

Place husks in a pot and cover with water. Bring to a boil, remove from heat and let soak for at least 30 minutes. Use a heavy plate to submerge husks in water.

Combine reserved braising liquid and broth in a medium saucepan and bring to a boil. Remove from heat.

Rehydrate masa harina. Place masa harina in a large heat-proof bowl and pour 6 cups of the broth over the 6 cups of masa harina. Stir until masa is evenly moist. If it is still really dry add another cup of broth. Save remaining for adding later. Cover bowl with plastic wrap until ready to let rehydrate.

Beat fat. Place 1 1/2 cups lard (or which ever fat you are using) in the bowl of a stand mixer fitted with a paddle attachment. Beat on high until light and fluffy, about a minute.

Add remaining ingredients. Add 1/2 cup minced cilantro, 2 tablespoons baking powder and 1 tablespoon salt and continue beating until light and fluffy, about a minute more. Turn off the mixer and scrape down the sides of the bowl with a rubber spatula.

Slowly add in masa. Turn mixer back on medium speed. Start adding rehydrated masa dough a handful at a time, letting it whip in before adding the next. You want to really beat the dough and incorporate a lot of air. Keep adding the masa until all the dough is added. Add more broth if necessary. Stop the mixer and feel the dough, it should be light and fluffy like whipped mashed potatoes, maybe even a bit wetter than that. If it is still too dry, add more broth, 1/2 cup at a time until it is almost soupy. It will stiffen as it sits so it is better to be on the wet side.

To Assemble: Fill a tamales steamer with water just until it reaches the rack where the tamales will sit. Use a few of the small or ripped soaked corn husks to line the rack. Cover and bring to a boil over medium-high heat. Once boiling, turn heat to medium and keep covered.

Dry a soaked corn husk with a clean kitchen towel. Hold the corn husk with the wide end toward you. Using a large spoon or tamale spreader, evenly spread about ½ cup masa from the middle of the husk down leaving about ½-inch border on the sides.

Place about 3-4 tablespoons of the beef mixture down the middle.

Fold one side of masa over the filling until the two edges of the corn husk meet, and holding onto one side of corn husk, pull the other side toward the middle to press the two edges of masa together. Fold the pointy end of the corn husk up over the large end, and place on a clean baking sheet. Repeat with remaining corn husks, masa, and filling. You can use a piece of corn husk to tie the tamales and prevent them from opening, but it is not necessary.

Place tamales vertically, open-side up in the tamale steamer, keeping them snug in the pot so they don't unravel during cooking. Make sure water is at a steady simmer and producing lots of steam. Cover tightly and steam until masa is cooked through and not doughy in the middle, about 1 hour. Check occasionally and add more water if the pot looks dry.

Remove from heat and let sit, covered, 5 to 10 minutes before removing from the pot. Tamales can also be left in the pot, covered with a clean towel (and then covered with the steamer lid) for up to an hour before serving. They will stay warm and soft if you want to make them in advance.