Mix together the miso paste, ginger and tamari and place in a large heatproof container or thermos flask.
Spiralise the courgette and place on top of the miso mix, then layer up the mushrooms, spring onions and rice noodles. Finish with the prawns.
When it's time for lunch, boil 250 milliliters of water in a kettle until almost boiled then pour it into the jar and stir well to combine the flavourings, veg, noodles and prawns.