Mix a marinade out of the oil, soy sauce, sugar and mustard and let the meat, bell pepper and onion marinate for at least an hour. Put the meat cubes, the paprika cubes and the onion slices alternately on skewers and grill or fry in the pan for 8 to 10 minutes.
Mix the marinade with the juice, add the chives and serve as a sauce. You can also leave out the sauce!