Place the rice in a pan with 2 ½ cups of cold water and a pinch sea salt. Bring to the boil and reduce to simmer for 30 - 35 minutes until cooked.
In a food processor grind half the cooked rice until it becomes sticky and glues together. Add it to a bowl with the remaining rice, vegetables, and sesame oil.
Using your hands take a small amount of the rice and veggie mix and make a ball the size of a 50 cent piece. Push index finger through to centre and place a dob of umeboshi and close up the ball.
Continue this process until all the rice mix has been used. Roll each ball in the sesame seed and wind a strip of damp nori around each ball.
Brush each ball with sesame oil.
Place the balls on a baking sheet lined with baking paper and bake in the oven for 15 minutes at 160C.
Serve with a dipping sauce of tamari.