Step 1

Heat the sesame oil in a large skillet over medium heat. Add the mushrooms and saute until golden brown, about 5 minutes. Add the cabbage and cook for another 8-10 minutes, until the cabbage is soft and the pan begins to look dry. Add the hoisin sauce, onion flakes, Sichuan pepper, scallions, garlic powder, and ginger; stir well. Set aside to cool.

Step 2

Meanwhile, prepare the dipping sauce by combining the soy sauce, vinegar, red pepper flakes, and remaining dried scallions in a small, shallow serving bowl. Arrange the gyoza wrappers in a single layer on two parchment-lined baking sheets. Place a small bowl of water next to the baking sheets.

Step 3

Once the filling is cool enough to handle, place one teaspoon of filling in the center of each gyoza wrapper. Dip a finger in the water and run it along the entire edge of the round wrapper closest to you. Form the potsticker by bringing two sides of the wrap together to form a half moon shape. Begin by pinching the center of the potsticker and work your way from the center out to both sides, pinching to create a seal as you go. Place the completed potsticker back on the baking sheet. Repeat with remaining wrappers.

Step 4

Heat the vegetable oil in a large skillet with a lid over medium heat. Working in batches, add potstickers in a single layer and allow to cook for 1-2 minutes, until they begin to brown. Add 1/2 cup of water to the pan and shake gently to loosen the potstickers from the bottom of the pan. Cover and allow to steam until the dough is cooked, about 3 minutes. Transfer to paper-towel lined plate and repeat with remaining batch of potstickers. Serve with dipping sauce.