Combine 16 cups water, 3 tablespoons salt, and beans in Dutch oven; bring to boil over high heat. Remove from heat, cover and let stand for 1 hour. Drain and rinse well.
Adjust oven rack to lower-middle position and heat oven to 300 degree F.
(CHILI PASTE STARTER) Toast ancho chiles in cast iron skillet over medium-high heat, stirring frequently until fragrant. Reduce heat if chiles start to smoke. Transfer to food processor and allow to cool. Do not wash skillet.
To food processor, add árbol chiles, cornmeal, oregano, coriander, cocoa, and 1/2 tsp salt; process until finely ground, about 2 minutes.
With processor running, slowly add 1/2 cup of the chicken broth until the chile powder turns to a paste. Transfer this paste to a small bowl.
In the still heated skillet, roast the jalapeños and habañero until skin of the vegetables browns and peels slightly. Add these to the processor with the onions and pulse until the consistency of chunky salsa, scraping down bowl as necessary.
(CHILI BASE) Heat 1 tablespoon oil in Dutch oven over medium-high heat. Add onion mixture and cook until moisture evaporates and vegetables soften. Stir occasionally. Add garlic and cook until fragrant. Add chili paste, tomatoes, and agave nectar. Stir until paste is incorporated. Add remaining 2 cups broth and drained beans; bring to boil then reduce heat to simmer.
Meanwhile, pat cubed beef and pork dry and sprinkle with salt. Heat 1 tablespoon oil in the same skillet and cook meat in batches until browned on all sides. In between batches, add the beer to the pan and scrape up browned bits and pour into Dutch oven with other ingredients. Transfer each batch of meat to the chili ingredients as you cook. Once last addition of beer and cooked bits are added to the Dutch oven, add in Tajin, stir to combine and return mixture to simmer for a few minutes.
Cover pot; transfer to oven. Cook until meat and beans are fully tender, about 2 hours. For best flavor, allow to cool about an hour and then leave overnight in the refrigerator. Reheat and enjoy with your favorite cheese (or substitute) and corn chips or crackers. It can be refrigerated for up to 3 days.