In a medium bowl, combine the ground pork, finely shredded napa cabbage, minced ginger, minced garlic, sliced green onion, tamari, and toasted sesame oil.
Mix the filling thoroughly by hand until the texture becomes slightly tacky and all ingredients are well incorporated.
Lay out the dumpling wrappers on a clean surface and place approximately one tablespoon of the pork mixture into the center of each.
Lightly dampen the edges of the wrappers with water, fold them over the filling, and press firmly to seal, creating small pleats along the edge.
Heat the avocado oil in a large non-stick skillet over medium-high heat until the oil is shimmering.
Arrange the dumplings in the skillet and sear for 2 to 3 minutes until the bottoms are a deep golden brown.
Carefully pour two tablespoons of water into the skillet and immediately cover with a tight-fitting lid to steam the dumplings for 5 minutes.
Remove the lid and continue to cook for another minute until the remaining moisture evaporates and the bottoms regain their crispness.
Whisk the rice vinegar with a small amount of extra tamari to serve as a bright dipping sauce on the side.