Combine the potato, onion, chicken stock, ginger, ground coriander and cumin in a pot and bring to the boil. Cover, reduce the heat to low and simmer for 30 minutes. Fish out the cube of ginger and discard it.
Add the fresh green coriander, green chilli, peas, salt, lemon juice and roasted cumin. Bring to the boil and simmer, uncovered, for 2–3 minutes or until