Combine pork, green onions, water chestnuts, ginger, soy sauce and sesame oil. Set aside. Place 1 potsticker skin at time on work surface. Lightly moisten around entire edge with small amount of water, then place I rounded teaspoon pork mixture in center of skin. Fold skin over filling and pinch closed at center of arc. Working to 1 side of center at time, seal edges by making 3 to 4 pleats toward center. Dumpling will form flatbottomed crescent with pleats across top. As you work, the dumpling will form a flat-bottomed crescent with pleats along the top. Heat 12-inch heavy or non-stick skillet with tight-fitting lid over medium-high heat. Add enough oil to coat bottom of pan generously. Arrange potstickers close together in circle around edge of pan, pleated edges up. Cook until bottoms begin to brown. Add water carefully to prevent spattering and immediately cover pan. Reduce heat to medium and cook 6 to 8 minutes, until potstickers are puffed and liquid is nearly evaporated. Remove lid and increase heat to medium-high. Cook until liquid boils away and potstickers begin to sizzle in remaining oil, then continue cooking until bottoms become crisp and browned, adding small amount of oil if necessary. Serve with soy sauce, sesame chile oil and hot Chinese mustard. Makes 18 potstickers. Each potsticker contains about 43 calories; 81 mg sodium; 3 mg cholesterol; 3 grams fat; 3 grams carbohydrates; 1 gram protein; 0.02 gram fiber.