Make the meatball mixture. Line a rimmed baking sheet with parchment paper, then preheat a broiler to high with an oven rack about 6-inches from the heating unit. In a large bowl, combine 1 lb ground pork, 1 large egg, ½ cup breadcrumbs, 2 Tbsp chopped mint, 2 cloves grated garlic, 2 tsp ginger paste, 1 Tbsp low-sodium soy sauce, 2 tsp sesame oil, and 2 tsp fish sauce. Use your hands to thoroughly combine.
Form the meatballs. Lightly wet your hands with water, then take about 2 tablespoons of the mixture at a time and roll into uniform spheres. Place on the prepared baking sheet. Repeat until all meatballs are formed.
Broil the meatballs. Place under a broiler, then cook for 5 minutes on the first side. Remove from the oven, carefully flip the meatballs over, and cook an additional 4-5 minutes on the second side. Note: the meatballs may not be fully cooked yet!
Meanwhile, make the broth. In a large pot, heat 2 Tbsp neutral oil over medium-high heat. Add half of the thinly sliced scallions and maitake mushrooms, stir, then cook undisturbed for about 3-4 minutes. Stir well, then continue cooking for another 2-3 minutes. Once the mushrooms have browned a bit, season with ½ tsp Kosher salt.
Add broth. Add 4 cups low-sodium chicken broth, then stir in the sliced ginger and 3 Tbsp dark soy sauce. Bring the mixture to a boil, then reduce to a simmer. Cook for 10 minutes.
Add meatballs to the broth. Stir in 2 Tbsp rice wine vinegar (or mirin), then taste and adjust seasoning as needed. Carefully add the meatballs to the broth and simmer for 5 minutes while they finish cooking.
Garnish, then serve. Meatballs can be enjoyed in bowls as is or spooned on top of rice or noodles. Before serving, sprinkle with a spoonful of chili oil, the remaining thinly sliced green onions, and fresh cilantro. Enjoy immediately with lime wedges on the side.