Dice the onion, bell pepper, and celery. Mince the garlic.

Heat the olive oil in a large pot or dutch oven over medium-high heat. Add the ground beef and cook, breaking it up, until well browned, about 8 minutes. Drain any excess fat.

Add the onion, bell pepper, and celery and cook 5 minutes, until they begin to soften. Stir in the garlic for 30 seconds.

Add the chili powder, cumin, smoked paprika, oregano, cocoa, salt, and pepper. Stir for 1 minute so the spices toast in the fat.

Stir in the tomato paste and cook 2 minutes, until it darkens slightly.

Add the crushed tomatoes and beef broth. Bring to a simmer, then lower the heat, partly cover, and simmer 30 minutes, stirring now and then.

Uncover and simmer 10 more minutes if you want it thicker. Taste and adjust the salt.

Ladle into bowls and top each with cheddar and a spoonful of sour cream.