Cook the potatoes in boiling salted water until tender, then mash them until they are quite smooth. Dissolve the sugar in the water in a saucepan over a fairly low heat. Sift the rice flour into a large bowl. Make a well in the centre, then add the mashed potatoes and sugar solution. Gradually stir in the rice flour then knead the mixture into a soft dough. Cover with cling film or a tea towel and chill. Prepare the filling. Soak the mushrooms in cold water for 15 minutes, then drain and steam them over boiling water for 15 minutes. Remove the mushroom stalks, then finely dice the caps. Finely dice the pork and marinate it with the soy sauce, 1/2 teaspoon of the sugar and 1/2 teaspoon of the sherry for 10 minutes. Soak and dice the dried shrimps. Heat the 2 tablespoons oil in a wok or frying pan. Add the pork, shallot and shrimps and fry for a while, then stir in all the remaining filling ingredients. Roll the dough into a cylinder shape, then cut it into 32 equal portions. Press the pieces of dough into flat circles and place a little filling in the centre of each. Draw up the edges of the dough, working it around the filling to seal
it in and make neat balls. Coat these completely in sesame seeds. Heat the oil for deep frying to 190 c/375 F, then add the sesame balls and deep fry them until golden brown. Drain and serve.