Prepare the corn husks: Add the corn husks to a large bowl or pot. Pour enough hot water over them to completely cover them. Cover the bowl with plastic wrap and let them soak for 1 hour to soften. Meanwhile, make the dough and prepare the filling.
Make the dough: In the bowl of a stand mixer, add the masa harina, salt, and baking powder. Mix briefly to combine. Add the canola oil and mix using the paddle attachment on medium-low speed. The dough should feel a little crumbly, almost like wet sand, and should lightly hold its shape when pressed together.
Slowly add the broth and mix for about 8-10 minutes on medium-high speed until the dough is fairly wet and well saturated. The dough should be soft, fluffy, and spreadable. If the dough is too dry, add more broth. If it's too wet, add more masa harina. Cover and set aside.
Make mole filling: In a large pot, heat the olive oil over medium heat. Add the tomatoes, onion, and garlic, and cook for 5-7 minutes until softened and starting to brown.
Add the guajillo and árbol chiles, the peanuts, and the Mexican chocolate. Sauté for an additional 2 minutes until the chiles are toasted and fragrant. Add the chicken broth, bring to a gentle simmer, reduce the heat to low, cover, and cook for 15 minutes.
Transfer everything to a large blender, and add the mole paste, salt, cumin, and peppercorns. Blend for several minutes until smooth.
Pour the mole sauce into a large pot and stir in the shredded chicken. Cook on medium-low heat for 5 minutes, then set aside.
Finish prepping the corn husks: Drain the water from the corn husks and pat them dry. Remove and discard any corn silk that may be on the husks. Lay the husks flat onto a baking sheet for easy access.
Spread the masa: Grab a corn husk and identify which is the smooth side and which is the side with ridges. Place the smooth side face up into your palm or on a plate. Using a large spoon, grab a heaping spoonful of masa and place it in the middle of the corn husk. Using the back of the spoon, spread the masa in a thin layer to create a rectangle shape, leaving the top ⅓ of the corn husk empty.
Add the filling: Spoon 1 ½ -2 tablespoons of mole filling into the center of the corn husk.
Fold: Fold together the long edges of the corn husk like a book, and then fold it once more. Fold the pointy edge over so that only one side of the corn husk is open and exposed. Place in a bowl with the open end facing up, making sure to lean them against the side so it doesn't fall down. Repeat until all the tamales have been filled and assembled.
Prepare the steamer pot: Fill the bottom of the steamer pot with water and cover with the steamer insert. Place the tamales in the steamer with the open end facing up, making sure to lean them against the side of the pot so they don't fall down.
Steam: Cover tightly with the lid and place the steamer over high heat. Bring the water in the steamer pot to a boil (you should be able to hear it bubbling), then reduce the heat to low, and cook for 1 hour to 1 hour and 15 minutes. To test if the tamales are ready, remove one from the pot and let it cool slightly for 5 minutes. Carefully peel back the husk. If the masa separates cleanly from the husk, then they’re ready.
Rest and serve: Carefully transfer the tamales to a baking sheet or serving platter and let them sit and cool slightly for 10 minutes. They may be a little squishy when you first take them out of the steamer, but will quickly firm up once they have time to cool. Serve and enjoy!
Mixing by hand. You can definitely make the masa dough without a stand mixer, it just requires some arm muscle. Mix together the dry ingredients, then incorporate the oil until the mixture is crumbly. Slowly add the chicken broth until well combined then continue mixing vigorously by hand for 8-10 minutes until light and fluffy.
Using lard. You can swap the canola oil for an equal amount of lard for a more traditional, richer flavor.
Storage and reheating. Store leftover tamales in an airtight container in the fridge for up to 1 week. To reheat, steam them for 15 minutes, warm them in a 350°F oven for 10 minutes, heat them on a hot griddle for 2 minutes per side, or microwave in batches for 1–2 minutes. They freeze beautifully, too. Just wrap them well and freeze for up to 6 months.