Pan-fry the potstickers. Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the frozen potstickers in a single layer and cook undisturbed for 2–3 minutes until the bottoms are golden and crispy. Add 1/4 cup of water, cover immediately, and let them steam for 4–5 minutes. Remove the lid and let any remaining water evaporate. Transfer potstickers to a plate and set aside.

Make the sauce. While the potstickers cook, whisk together soy sauce, rice vinegar, hoisin sauce, sesame oil, brown sugar, and red pepper flakes in a small bowl. Stir in the cornstarch slurry and set aside.

Stir-fry the veggies. In the same skillet, heat the remaining tablespoon of oil over high heat. Add the white parts of the green onions, garlic, and ginger. Stir-fry for about 30 seconds until fragrant. Add the cabbage, carrots, and bell pepper, and cook for 2–3 minutes, stirring frequently. You want them slightly softened but still with a little crunch.

Bring it all together. Pour the sauce over the vegetables and stir to coat. Add the potstickers back into the pan and gently toss everything together. Cook for another 1–2 minutes until the sauce thickens and coats everything nicely.

Serve and garnish. Divide into four bowls, top with sesame seeds, green onion tops, and a drizzle of sriracha if you like a little heat. Serve immediately.