In a bowl, mix the asparagus with all the other ingredients up to and including the salt, transfer to a baking tray lined with baking paper.
Approx. 20 mins. in the centre of an oven preheated to 200°C. Add the cashew nuts, mix, cook for a further 15 mins.
Add the barley to boiling salted water, reduce the heat, simmer for approx. 25 mins. until just soft, drain.
Whisk together the mustard, balsamic and oil in a bowl, season. Add the pearl barley, mix. Mix in the asparagus, herbs and reserved onion greens.