How to Make It
In a small skillet, toast the sesame seeds over moderately high heat for 30 seconds, shaking the pan, until lightly browned. In a small bowl, stir the soy sauce with the vinegar, water, garlic, scallion and toasted sesame seeds.
Line a large baking sheet with parchment paper. In a large bowl, combine the ground pork with the kimchi, scallions, egg, cornstarch, sugar, soy sauce, salt and pepper. Using your hands, mix the dumpling ingredients thoroughly.
Place 4 gyoza wrappers on a work surface; keep the rest covered with plastic wrap. Lightly moisten the edges of the gyoza wrappers with water. Place a level tablespoon of the ground pork and kimchi filling on one side of each wrapper and fold in half to form half-moons. Press the edges of the wrapper firmly to seal, making pleats for decoration. Lift each dumpling by the pleated edge, transfer it to the baking sheet and press down lightly to flatten the bottom; the dumpling should be standing with the pleat side up on the baking sheet. Repeat with the remaining gyoza wrappers and pork and kimchi filling.
In a large, nonstick skillet, heat 1 tablespoon of the oil. Add half of the pot stickers to the skillet, flattened side down. Pour in 1/2 cup of the water, cover and cook over moderately high heat until the water has evaporated, the filling is cooked through and the bottoms are browned, 8 to 10 minutes. Transfer to a serving platter and keep warm. Wipe out the skillet and repeat with the remaining oil, pot stickers and water. Serve with the dipping sauce on the side.