Slice kumara into ½ cm (¼ in) thick slices and steam or boil until just cooked. Season well and put to one side.
Halve chorizo lengthways or cut into 1 cm (½ in) rings. Heat a frying pan or barbecue and brown chorizo for 1 minute on both sides, taking care that they don’t burn. Split rolls and drizzle both halves with a little olive oil. Spread a little chutney on the bottom halves. Lay kumara on top, then rocket, chorizo, a good dollop of chutney and finally the lids.