Preheat the oven to 375°F and line a baking sheet with parchment paper.
In a mixing bowl combine the ground chicken, chopped green onions, chopped cilantro, 1 tablespoon fish sauce, 1 tablespoon red curry paste, breadcrumbs, the egg, 1/4 teaspoon salt and 1/4 teaspoon pepper; stir just until evenly combined without overmixing.
Form the mixture into small 1-inch meatballs and place them on the prepared baking sheet about 1/2 inch apart.
Bake the meatballs for 18–20 minutes, until cooked through and no longer pink in the center.
While the meatballs bake, heat the sesame oil in a medium saucepan over medium heat and cook 1 tablespoon red curry paste for 1–2 minutes until fragrant.
Add the coconut milk, peanut butter, brown sugar, red pepper flakes, and 1/4 teaspoon salt and 1/4 teaspoon pepper to the pan; stir and simmer for about 5 minutes until smooth and slightly thickened.
Transfer the baked meatballs into the sauce and gently toss to coat evenly, warming together for 1–2 minutes.
Serve hot garnished with additional cilantro if desired.