In a large mixing bowl, combine the ground turkey, chopped green onions, cilantro, fish sauce, red curry paste, breadcrumbs, egg, salt, and black pepper. Mix until well incorporated, but be careful not to overmix.
Using your hands, form the mixture into meatballs, about 1 to 1.5 inches in diameter. Place them on a baking sheet lined with parchment paper.
Preheat your oven to 400°F (200°C). Bake the meatballs for 20-25 minutes, or until they are golden brown and cooked through.
While the meatballs are baking, heat the peanut oil in a large skillet over medium heat. Add the red curry paste, lemongrass paste, grated ginger, and minced garlic. Sauté for about 2 minutes until fragrant.
Pour in the chicken broth and coconut milk. Add the kaffir lime leaves and sugar. Stir well to combine, and let it simmer for about 5-7 minutes, allowing the flavors to meld together.
Once the meatballs are cooked, carefully transfer them to the skillet with the curry sauce. Gently toss to coat the meatballs in the sauce and let them simmer for an additional 5 minutes.