Pat the chuck roast chunks dry with paper towels. Generously coat the beef with neutral oil, then season all over with the garlic powder, onion powder, smoked paprika, Mexican oregano, cumin, ancho chili powder, light brown sugar, kosher salt, and black pepper.
Heat a large skillet or Dutch oven over medium-high heat. Add a small amount of neutral oil if needed, then sear the seasoned beef in batches, making sure not to overcrowd the pan. Sear for about 2–3ish minutes per side, or until a nice crust forms on the outside. Transfer the seared beef to the slow cooker.
In the same skillet, add the diced yellow onion and cook for about 2–3 minutes, until it begins to soften and the onions are translucent. Add the minced garlic and cook for another 30 seconds, stirring frequently. Be careful not to burn.
Transfer the onions and garlic to the slow cooker with the seared beef.
Add the diced fire-roasted tomatoes, tomato sauce, green chilies, and cocoa powder to the slow cooker. Stir well to combine and evenly distribute the cocoa powder throughout the chili.
If using pinto beans, drain and rinse them, then add them to the slow cooker. Gently stir to combine.
Cover and cook on LOW for 7–8 hours or HIGH for about 4–5 hours, or until the beef is tender and easily pulls apart with a fork.
Taste the chili and adjust the seasonings as needed. Serve with your favorite toppings, enjoy!