Gyoza Japanese Dumplings

Name: Gyoza (Japanese Dumplings)
Ingredients: 1 packet 50 gyoza wrappers; 1/8 cabbage; 1 teaspoon salt; 400 g lean pork or chicken; 1/2 bunch garlic chives, finely chopped; 4 dried shiitake mushrooms, soaked in hot water and finely chopped; 1 tablespoon grated ginger; 2 teaspoons soy sauce; 2 teaspoons sesame oil, plus 2 teaspoons extra, for cooking; Pinch of salt; 2 tablespoons soy sauce; 2 tablespoons rice vinegar; La-yu (Japanese chilli oil), optional