For the best result, cook the beef in two batches. Heat half of the oil in a non-stick wok or frying pan until very hot then add half the beef, stir fry for 2 -3 minutes until brown, remove to a plate and repeat with the remaining beef.
Return to the wok or frying pan and heat the remaining oil. Fry the onion until it begins to soften, then add the red pepper and courgette, cook for a minute stirring continuously.
Pour chopped tomatoes, cherry tomatoes, dissolved stock cube in water, garlic, sugar and balsamic vinegar into the pan and bring to the boil, then reduce the temperature and simmer for 5 minutes.
Return the cooked beef to the pan along with Cannellini beans and chopped parsley, cook for about 3 minutes before serving with crusty bread.