In a large bowl, combine the ground pork, cabbage, green onions, garlic, soy sauce, sesame oil, and cornstarch. Mix well.
Place a spoonful of the pork mixture in the center of each dumpling wrapper. Moisten the edges of the wrappers with water and fold the wrappers in half to form half-moon shapes, sealing the edges well.
Heat a large pan over medium heat. Add the potstickers to the pan in a single layer and cook for 2-3 minutes, until the bottoms are browned. Add 1/2 cup of water to the pan, cover, and steam the potstickers for an additional 2-3 minutes, until the pork is cooked through. Remove the potstickers from the pan and set aside.
In the same pan, bring the chicken broth, water, soy sauce, rice vinegar, sesame oil, and chili garlic sauce (if using) to a boil. Add the potstickers to the broth and simmer for an additional 2-3 minutes.
Serve the soup hot, garnished with additional green onions if desired.