Heat a large Dutch oven over medium-high heat.
Add the pancetta; cook and stir until browned then set aside. Add half of the olive oil to the Dutch oven and allow it to get hot. Add the beef cubes, season with salt and pepper and cook until browned on all sides. Add the vinegar and whisk up all of the browned bits from the bottom of the pan; set aside with the pancetta.
Heat the remaining oil in the Dutch oven; add onions and garlic and cook until onions have softened.
Return beef/pancetta mixture to the Dutch oven along with next 6 ingredients (broth through chocolate); season with salt and pepper.
Bring mixture to a boil then reduce heat, cover and simmer for 1 hour or until beef cubes are fork-tender. Remove cinnamon sticks and serve.