Ingredients (Serves 2)
For the sauce
First make the sauce. Place all the ingredients in a pan over a low heat.
Bring to just below boiling point then strain and keep warm.
Heat a medium pan of oil, 8-10cm/ 31⁄4-4in deep, to a temperature of 180°C, 350°F. Season the mackerel with salt then dust in the arrowroot. Fry in the hot oil for 2-3 minutes. Remove and drain on kitchen paper.
Fry the spring onions for 30 seconds. Remove and drain on kitchen paper. Add the coriander and parsley sprigs to the hot sauce for a few seconds to soften them.
Arrange the steamed bok choi in the base of a dish. Place the mackerel on top and pour a little sauce over. Arrange the coriander, parsley and onion on top of the fish. Scatter with the chopped cashews before serving.