In a large skillet over medium-high heat, combine ground beef and diced onion. Cook until beef is no longer pink and onions are translucent, about 6-8 minutes. Add minced garlic and sauté for an additional 1-2 minutes until fragrant. Drain excess grease and transfer to the slow cooker.

Add the beef mixture to the Crockpot. Add rinsed kidney beans, black beans, diced tomatoes with juice, tomato sauce, and beef broth. Stir gently to combine the ingredients evenly.

Sprinkle in chili powder, ground cumin, smoked paprika, dried oregano, unsweetened cocoa powder, salt, and pepper. Mix thoroughly to incorporate the spices into the chili.

Set the slow cooker to low and cover, cooking for 6-8 hours. Alternatively, cook on high for 3-4 hours.

Once cooking time is complete, stir the chili before serving. Scoop into bowls and top with options like shredded cheese, sour cream, or fresh cilantro.