Preheat the oven to 425°F. Line a baking sheet with parchment paper.
In a large mixing bowl, combine the ground beef, panko breadcrumbs, egg, milk, soy sauce, green onions, garlic, ginger, salt, and pepper. Mix gently until just combined.
Roll the mixture into approximately 24 meatballs and place them on the prepared baking sheet.
Bake for 14 to 16 minutes, or until the meatballs reach an internal temperature of 160°F.
While the meatballs bake, heat a large skillet over medium-high heat. Add the pineapple chunks and cook for 2 to 3 minutes until lightly caramelized. Transfer to a plate.
In a medium saucepan, combine the pineapple juice, soy sauce, brown sugar, honey, rice vinegar, garlic, and ginger. Bring to a gentle simmer.
In a small bowl, whisk together the cornstarch and cold water until smooth. Stir the slurry into the simmering sauce and cook for 1 to 2 minutes until thickened.
Remove the sauce from the heat and stir in the toasted sesame oil.
Add the baked meatballs and caramelized pineapple to the sauce. Toss gently until evenly coated.
Return the pan to low heat and simmer for 5 minutes, allowing the flavors to meld.
Garnish with sliced green onions and toasted sesame seeds.
Serve hot over cooked white rice.