In a bowl, combine ground pork, cabbage, green onions, soy sauce, sesame oil, ginger, garlic, sugar, salt, and pepper. Mix until fully combined.

Place a small spoonful of filling in the center of each dumpling wrapper.

Moisten edges with water, fold in half, and press to seal, pleating if desired.

Heat vegetable oil in a large skillet over medium-high heat.

Arrange potstickers in a single layer.

Cook until bottoms are golden brown.

Add water and immediately cover.

Reduce heat to medium and steam until water evaporates and filling is cooked through.

Remove lid and cook briefly to re-crisp bottoms.

In a small bowl, combine soy sauce, rice vinegar, sesame oil, sugar, red pepper flakes, and green onions.

Stir until sugar dissolves.

Serve potstickers hot with dipping sauce.

Serve immediately while crisp.