Peel the sweet potato, cut into chunks and boil in salted water until tender.
While the potatoes are cooking, make the filling. Blend the dried prawns, lemongrass, shallots, garlic and chillies until fine. Heat a little oil in pan and fry the blended ingredients until fragrant. Add the grated coconut, tumeric and season with salt. Mix well and cook for another 3 minutes. Remove and set aside.
When the sweet potatoes are cooked, remove and mash them. Add the flour and knead into a soft dough. Divide the dough into equal portions. Take one portion and flatten it slightly, take a teaspoon of the filling and place in center and seal the cake.
Heat oil in wok until hot and deep fry the sweet potato cakes. Drain on paper towel and serve.