Cook the sushi rice following pack instructions. Tip out onto a plate, sprinkle with the rice vinegar and a little seasoning, then leave to cool.

Meanwhile, lay a piece of cling wrap on a work surface and put a nori sheet on top, place some rice on top and shape into an 8cm square in the middle of the nori sheet.

In single layers, add some of the carrot, avocado, mayo, prawn, ginger and cucumber on top. Shape another square of rice and place on top. Fold up the corners of the nori wrap to completely enclose the rice, using a little water to seal the sandwich completely, then wrap tightly in the cling wrap.

Repeat with the rest, then chill until needed. To serve, cut in half, sprinkle some black sesame seeds and serve with soy sauce for dipping.