1. Put peeled, quartered potatoes into a pan with 475 ml/16fl oz water and boil. Cover the pan and reduce heat to medium. Cook until tender. Reserve 150ml/1/4 pint of the liquid and discard the rest.
2. Heat the butter and oil over a medium-low heat; fry the onions until they begin to colour. This will take 8 to 9 minutes.
3. Add the spices, stir and cook for 30 seconds; add half the potato stock. Stir until all the liquid has evaporated.
4. Add the potatoes, salt and the remaining stock. Reduce the heat to low and cover. Cook for 5-6 minutes.
5. Stir in the herbs and remove from the heat. Pop into a serving dish and garnish with a little chopped coriander.