Place the rice basket on top of the Thermomix and weigh in the sushi rice. Rinse under cold water.
Place the water into the Thermomix bowl, insert the rice basket, secure the lid and cook for 20 minutes, Varoma, Speed 4.
Very carefully remove the rice basket from the Thermomix (it will be very hot!). Transfer the rice to a large plate. Drizzle over the sushi seasoning and fluff with a fork up and allow to cool slightly.
Place a sushi bamboo mat (these can be bought from the Asian section of the supermarket) onto a flat bench.
Place a nori sheet on top of the sushi mat with the rough side facing up. Sprinkle it with a tiny amount of water.
Spread a thin layer of cooked sushi rice (approximately ½ cup) over the sheet of nori (leaving a 2cm gap at the top of the sheet – to assist with sealing) and press down with the flat side of a spoon.
Place your filling in a thin line in the centre. Dampen the uncovered end of the nori sheet with water.
Start from the end without the gap and roll tightly together (it takes a bit of practice).
Cut into small pieces with a sharp knife and serve.