Cook the Aromatics
In a large pot, heat sesame oil over medium heat. Add the diced onion and cook for about 5 minutes until softened. Stir in the minced garlic and grated ginger, cooking for another minute until fragrant.
Prepare the Broth
Add chicken broth and water to the pot, stirring to combine with the aromatics. Bring the broth to a simmer, then add soy sauce, rice vinegar, and sugar. Let the broth simmer for 5 to 10 minutes to allow the flavors to blend. Taste and adjust the seasoning with more soy sauce or vinegar if necessary.
Add the Vegetables
Add the chopped napa cabbage (or bok choy), sliced carrots, and frozen peas to the broth. Cook for 3 to 5 minutes until the vegetables are tender but still vibrant.
Cook the Potstickers
Carefully drop the frozen potstickers into the soup. Let them cook for 8 to 10 minutes. The potstickers will float when they are done, but stir gently to prevent sticking.
Final Seasoning
Taste the soup and adjust seasoning with more soy sauce, vinegar, or salt if needed. If you like heat, now is the time to add chili oil for extra spice.
Serve
Ladle the soup into bowls, making sure each bowl gets a few potstickers. Garnish with chopped green onions, sesame seeds, and fresh cilantro. A drizzle of chili oil adds a spicy kick if desired.