Mix together beef onion and breadcrumbs. Season meat mixture with salt and pepper and divide into 30 bals. Flatten each ball out Place a piece of cheese in centre then mould meat around cheese sealing it well to enclose cheese completely. To make the tangy sauce put tomato paste, wine, vinegar, honey, mustard, Worcestershire sauce and stock into a saucepan and simmer for 10 minutes. Blend cornflour smoothly with orange juice then stir into the sauce and simmer for 1 minute stirring all the time. Serve with the meatballs cooked in the hot oil.