1. Gently combine chicken, garlic, ginger, scallions, cabbage, salt, baking powder, and cornstarch in a medium bowl. Do not overmix.
2. Place a wonton wrapper in your non-dominant hand. Use a knife to scoop out about a teaspoonful of the chicken mixture and place it into the center of a wonton wrapper. Smooth the filling with the knife so you have a small, smooth mound. Wet the edge of the wrapper; use both hands to pleat the top edge of the wrapper and seal it closed. Continue with remaining filling and wrappers.
3. Heat one-fourth cup of oil in a large frying pan with a cover and place the pot stickers into the hot oil. Cook for about two minutes over medium-high heat.
4. Carefully hold the cover in one hand and pour about three tablespoons of water into the pot with the other. Cover the pot immediately.
5. Cook for another two minutes, then uncover and finish cooking until the pot stickers release from the pan easily. Remove to a paper towel.
6. Combine soy sauce, rice vinegar, mirin, and sesame oil for dipping.