Mix the pork with the soy sauce, ginger, rice wine and salt. Add 150 ml of water and stir well mixing all ingredients. Add the leeks and sesame oil and blend well. Divide into 60 portions and set aside.
Stir 200 ml water into the flour. Knead until the dough is smooth and elastic. Cover and let rest for 30 minutes. Roll into a long cylinder and cut into 60 portions. Flatten each piece and roll into a circle about 3 inches (8 cm) in diameter. Place 1 portion of filling on each circle and fold. Pinch tightly to seal the edges and form a squat bonnet-shaped pouch. Repeat until all the dough and filling are used.
Arrange the pouches in a large pan. Heat to moderately hot, then add water to cover the pouches one-third of the way up. Cover the pan and cook over high heat until the water is almost absorbed.
Mix 2 tablespoons of water with 1 teaspoon flour and trickle around the pouches. Cover the pan and sauté over low heat until the flour forms a crisp film that links the dumplings together. Sprinkle the dumplings with a little sesame oil, cover again, and sauté until the pouches are browned on the bottom. Remove with a spatula and repeat this process until all dumplings are done.
