For the pickled cabbage, toast the coriander seeds in a dry frying pan over a low-medium heat until aromatic, then lightly crush using a pestle and mortar or the end of a rolling pin. Tip into a large, non-metallic bowl with the chilli flakes (if using), vinegar, orange juice, sugar and a generous pinch of salt. Stir until the sugar has dissolved, then add the onion and cabbage. Toss well, scrunching the cabbage lightly using your hands. Leave to lightly pickle for at least 1 hr. Will keep covered and chilled for up to a week – the cabbage will soften and the flavours will develop further the longer it sits.
