Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.
In a medium mixing bowl, combine the ground chicken, chopped green onions, chopped cilantro, 1 tablespoon fish sauce, 1 tablespoon red curry paste, breadcrumbs, egg, 1/4 teaspoon salt, and 1/4 teaspoon pepper. Stir just until evenly mixed; do not overmix.
Form the mixture into small 1-inch meatballs and arrange them on the prepared baking sheet, leaving a little space between each.
Bake the meatballs for 18–20 minutes, or until cooked through and lightly browned.
While the meatballs bake, heat 1 tablespoon sesame oil in a medium saucepan or skillet over medium heat. Add 1 tablespoon red curry paste and cook, stirring, for 1–2 minutes until fragrant.
Add the 14-ounce can of coconut milk, 2 tablespoons peanut butter, 1 tablespoon brown sugar, 1/4 teaspoon red pepper flakes, 1/4 teaspoon salt, and 1/4 teaspoon pepper to the pan. Stir to combine and simmer for about 5 minutes until slightly thickened.
Transfer the baked meatballs into the sauce and gently toss to coat them completely. Cook together for 1–2 minutes to warm through.
Garnish with chopped cilantro or parsley if desired and serve.
