Southern potato curry, two ways

Method

1. Halve the potatoes and boil until just tender, (they will break up in the sauce if overcooked now). I prefer to boil them in their skins, to minimise the amount of water they absorb, then peel them before continuing.
2. Meanwhile, heat the oil in a large saucepan and add the mustard and cumin seeds, the lentils and cinnamon stick. Once the popping of the mustard seeds has died down, add the curry leaves (if using). Follow immediately with the onions and cook until soft and lightly golden.
3. Add the ginger, tomatoes, chilli, coriander, fennel, turmeric and salt and stir-fry over a high heat for three minutes. Add 200ml water, bring to a boil and simmer gently for 10 minutes. Add the cooked potatoes to the sauce to absorb the flavours for five minutes, or until the liquid in the pan has dried up.
4. Add the coconut milk (if using) and enough water to get a medium consistency sauce. Taste, adjust the seasoning and stir in the chopped coriander. Serve.