1. First make the spice paste. Either use a pestle and mortar or blender to grind all the ingredients into a smooth paste.
2. Heat the oil in a heavy bottomed saucepan and sauté the spice paste until fragrant.
3. Now add the sweet potato, stock and coconut milk.
4. Bring to the boil, then simmer until the potatoes are almost fork tender.
5. Then add the beans and continue to cook for a few more minutes until the beans are heated through.
6. Garnish with the coriander and serve with steamed rice.