For the skin: Combine both types of flours in a mixing bowl. Make a well in the centre and pour in boiling water. Stir quickly to mix with a small and short rolling pin. Cover and leave aside for 5 to 10 minutes. Add shortening and knead till dough is smooth.
Roll out into a tube. Lightly grease a cleaver and cut into equal pieces. Flatten each piece with the cleaver to a round shape. Place 1 tsp filling in centre of wrapper. Pleat to form a meat dumpling.
Arrange dumplings on a greased steaming tray and steam for 5 to 10 minutes. Brush with a little oil and serve immediately.
Filling: Steep prawns in 1/2 tbsp alkaline water for about 5 minutes then place prawns in a metal sieve and rinse in running tap water for about an hour. (this makes the prawns crunchy.) dry the prawns thoroughly on a tea towel.
Mix prawns with 1/2 tsp salt and 1/2 tbsp tapioca flour. Rub flour in well. Add the rest of the ingredients and the seasoning ingredients. Chill mixture till it is almost hard.