To prepare the filling, place the pork fat in the boiling water and boil until fully cooked and translucent, about 30 minutes. Remove, place in a bowl, run cold water over it, and allow to stand for several minutes. Remove, dry with paper towels, and cut 2 tablespoons of fat into 1/8-inch dice. Reserve. Place the shrimp in the bowl of a electric mixer. Start the mixer and add, mixing thoroughly after each ingredient, the salt, sugar, egg white, tapioca flour, oyster sauce, sesame oil, and white pepper. Add the pork fat, water chestnuts, scallion, and bamboo shoots. Combine evenly and thoroughly. Remove the mixture, place in a shallow dish, cover, and refrigerate for 4 hours or overnight. To make the dough, in the bowl of an electric mixer, place the wheat starch, tapioca flour and salt. Start the mixer and add the boiling water. (If an electric mixer is unavailable, mix by hand in the same order, pouring water with 1 hand, mixing with a wooden spoon with the other.) Add the lard and mix thoroughly. If the dough is too dry, add 1 teaspoon boiling water. Continue to mix until a ball of dough is formed. Remove from the bowl, knead a few times, and divide into 4 equal pieces. Place each piece in a plastic bag to retain moisture. To prepare the dumplings, before working the dough, oil the work surface. Soak a paper towel in melted pork fat or peanut oil and repeatedly run a clever blade across it so that the blade stays oiled. Roll each piece of dough into a cylinder 8 inches long and 1-inch in diameter. Cut into 1/2-inch pieces. Work with one and keep the others covered with plastic. Roll each into a small ball and press down with your palm to flatten it. Press flatter with the broad side of the oiled cleaver to create a round skin 2 1/2 inches in diameter. To form the dumplings, place 1 1/2 teaspoons of the filling in the center of each round and fold in half, forming a crescent or half moon. Hold the dumpling securely in one hand, then begin to form pleats with the fingers of the other hand. Continue to form small pleats until the dumplings are completely closed. Press the top edge of the dumpling between your thumb and forefinger to seal tightly. Tap the sealed edge lightly your knuckle to give the dumpling its final shape. Oil a steamer, place the har gau into steamer, cover, and steam for 7 minutes. Turn off the heat and serve.;
Recipe courtesy of Eileen Yin-Fei Lo, "The Chinese Kitchen"