Start by cubing the tuna very small and place in a large mixing bowl.
Now add 1 tablespoon of sesame oil, 1 tablespoon of sesame seeds, 1 tablespoon sesame oil, the spring onions and the juice of 1 lime and stir well, chill for at least an hour.
Meanwhile take a wok and get really hot, now add the cabbage and cook for a minute or so then add a tablespoon of sesame oil and cook for 3-4 minutes. Now add a tablespoon of soy sauce, the juice of a lime and a tablespoon of sesame seeds and take off the heat. Let cool and add to the tuna mix and stir well.
To serve place some tuna mix into metal rings to give a good shape on your plate.