Heat the olive oil in a large pot and sauté the meat for 7-8 minutes. Slowly pour the vinegar and then the wine. Add the remaining ingredients except for the vegetable oil, onions and sugar, cover and cook for 1 hour at a low heat or until the meat is almost tender.
Heat the vegetable oil in a frying pan and add as many onions in one layer as it will take. Sautee them gently for about 15 minutes, shaking and turning them until they brown lightly. Take them out of the pan and spread them over the meat, distributing them evenly. Repeat until all the onions are done. Sprinkle the onions with ethe sugar, cover the pot and cook at a low heat for 30 minutes, until the onions are soft but not disintegrating.
Do not stir once the onions have been added, but instead rotate the saucepan occasionally to coat them in the sauce.
