Preheat oven to 160°C Heat a large flameproof casserole dish over high heat. Add the pancetta and cook, stirring, for 2-3 minutes or until golden. Transfer to a heatproof bowl. Add 60ml (1/4 cup) of the oil to the casserole dish. Add one-quarter of the beef and cook, turning, for 5 minutes or until brown. Transfer to the bowl with the pancetta. Repeat, in 3 more batches, with the remaining beef, reheating the dish between batches.
Add the vinegar to the dish and cook, stirring to dislodge any bits that have cooked on to the base, for 1-2 minutes. Pour over the beef mixture.
Heat the remaining oil in the dish over medium heat. Add the onion and garlic and cook, stirring, for 10 minutes or until soft. Add the beef mixture, stock, wine, tomato paste, cinnamon, thyme, orange peel and chocolate. Cover with foil and a tight-fitting lid. Bring to the boil. Bake in oven for 2 hours or until the beef is tender. Set aside for 15 minutes to cool. Place in the fridge for 6 hours to chill.
Preheat oven to 160°C Use a spoon to remove any fat from the surface of the stew. Cook the stew, stirring, over low heat for 5 minutes or until heated through. Bake in oven for 45-50 minutes or until the meat is tender and the sauce thickens. Sprinkle the stew with parsley to serve.