In a large bowl, gently combine the ground chicken, panko breadcrumbs, chopped onion, egg, soy sauce, ginger, garlic, and pepper. Be careful not to overmix.

Roll the mixture into 1-inch meatballs. Use a small cookie scoop to ensure they are all the same size.

Preheat oven to 400°F (200°C). Place the meatballs on a baking sheet lined with parchment paper. Bake for 15-20 minutes, or until cooked through. Alternatively, heat a tablespoon of oil in a large skillet over medium heat. Add the meatballs and cook, turning occasionally, until browned and cooked through, about 10-12 minutes. Another option is to preheat your air fryer to 375°F (190°C). Place the meatballs in the air fryer basket in a single layer. Cook for 10-12 minutes, or until cooked through.

In a medium saucepan, whisk together the pineapple juice, soy sauce, brown sugar, and rice vinegar.

In a small bowl, whisk together the cornstarch and water to form a slurry. Add the slurry to the saucepan.

Bring the sauce to a simmer over medium heat, stirring constantly. Cook for 2-3 minutes, or until the sauce has thickened.

Stir in the diced pineapple chunks, sesame oil, ginger, garlic, and red pepper flakes (if using). Cook for another minute until fragrant.

Add the cooked chicken meatballs to the saucepan with the pineapple teriyaki sauce. Gently toss to coat the meatballs evenly.

Simmer for 5-10 minutes, allowing the meatballs to absorb the sauce and the flavors to meld together.

Transfer the Pineapple Teriyaki Chicken Meatballs to a serving dish.

Garnish with sesame seeds and chopped green onions.

Serve hot as an appetizer or over rice for a complete meal.