Heat a dry cast iron skillet over medium heat and toast the ancho, guajillo, and pasilla chiles for 2–3 minutes per side until fragrant and slightly darkened. Transfer to a heat-safe bowl, cover with boiling water, and soak 20–30 minutes until pliable; reserve 1 cup (240 ml) of the soaking liquid before draining.
Add the softened chiles to a food processor along with 1 cup (240 ml) reserved soaking liquid, 4 cloves of the minced garlic, 1 tablespoon cumin, and 1 teaspoon salt; process on high for 2–3 minutes until completely smooth. Set the paste aside.
Pat the beef cubes dry with paper towels, then season all sides with 1 teaspoon kosher salt and 1 teaspoon black pepper. Let the beef rest at room temperature for 10–15 minutes before searing.
Heat 1 tablespoon oil in your Dutch oven over medium-high heat and sear the beef in uncrowded batches, 2–3 minutes per side, until deeply browned. Transfer to a plate and repeat with remaining beef.
Reduce heat to medium, add the remaining tablespoon of oil, and cook the diced onion for 5–7 minutes until softened. Add the remaining garlic, the remaining 1 tablespoon cumin, smoked paprika, oregano, coriander, cayenne, and cinnamon; stir for 1–2 minutes until fragrant.
Pour in the beer and scrape up any browned bits from the bottom of the pot; simmer 2–3 minutes. Stir in the chile paste, return the seared beef with its juices, add 3 cups (720 ml) broth, apple cider vinegar, and brown sugar, then bring to a boil.
Reduce heat to low, cover the pot with the lid slightly ajar, and simmer gently for 2–3 hours, stirring every 30 minutes, until the beef is fork-tender and the sauce has thickened.
Whisk the masa harina into the remaining 1 cup (240 ml) broth until smooth, then stir it into the chili along with the chopped dark chocolate. Simmer uncovered for 20–30 minutes, taste and adjust seasoning, then rest for 10–15 minutes before serving.