Heat oil in a saucepan and cook onion over a moderatehigh heat until it begins to caramelise. Add chorizo, garlic and ginger and cook 1–2 minutes to release the fat from the chorizo. Add remaining ingredients except spring onions and bring to the boil. Stir, cover and simmer until kumara is just cooked, 8–10 minutes. Remove lid, gently stir again and cook 4–5 minutes to reduce liquid. Just before serving, stir in spring onions.