Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add the diced onion and cook until softened and translucent, about 5-7 minutes.

Stir in the minced garlic and chipotle peppers. Cook until fragrant, about 1 minute.

Add the tomato paste and cook, stirring constantly, until it deepens in color to a brick red, about 2-3 minutes. This caramelization enhances its flavor.

Add the ground beef to the pot. Break it up with a spoon and cook until browned. Drain off any excess fat.

Stir in the chili powder, cumin, cocoa powder, smoked paprika, oregano, and cayenne pepper (if using). Cook, stirring, for 1 minute until the spices are fragrant.

Pour in the beef broth, crushed tomatoes, and add the rinsed black beans. Stir everything together, scraping up any browned bits from the bottom of the pot.

Bring the stew to a simmer, then reduce the heat to low, cover, and cook for at least 30 minutes, stirring occasionally, allowing the flavors to meld.

Uncover and stir in the brown sugar and apple cider vinegar. Continue to simmer for another 10-15 minutes, or until the stew has thickened to your desired consistency.

Season generously with salt and black pepper to taste. Serve hot with your favorite toppings.