Heat a large Dutch oven or soup pot over medium-high heat. Add olive oil, onion, garlic, bell pepper, & ground beef. Sauté 8-10 minutes, or until beef is browned.
Add to pot brown sugar & the following 9 ingredients (through beef broth). Stirring to combine & bring to a boil. Reduce heat. Cover & simmer 15-20 minutes, or until slightly thickened, stirring occasionally.
Add chopped chocolate, stirring to melt. Ladle into soup bowls & top with sour cream. Garnish with green onions.