Heat 1 tablespoon of oil in a large stockpot over medium-high heat, then sauté the mushrooms until browned. Add the remaining 1 tablespoon oil, garlic, and ginger, cooking for 1-2 minutes until fragrant.

Pour in vegetable broth and soy sauce, stir to combine, and bring the mixture to a boil. Add frozen potstickers, half of the scallions, and bok choy, cooking for 3-4 minutes until the potstickers are done, then stir in sesame oil and black pepper, adjusting seasoning if needed.

Serve the soup immediately, garnished with the remaining scallions and any preferred optional toppings.