In a bowl, combine the ground chicken or pork, ground beef, chopped scallions, panko, garlic, ginger, salt, sugar, and sesame oil. Mix thoroughly until everything is evenly distributed.
Roll the meat mixture into half-inch balls and set them aside.
For the teriyaki sauce, combine the dark soy sauce, light soy sauce, honey, garlic, ginger, sugar, and sesame oil in a small pot and bring to a simmer. Stir the cornstarch and cold water together, add the slurry, and remove from the heat once the sauce has thickened.
Heat a pan over medium heat with a bit of oil. Add the meatballs and cook for about 10 minutes, rotating constantly so they brown on all sides.
Pour in the teriyaki sauce and glaze the meatballs, removing them from the heat once the sauce starts to caramelize.
Serve over a fresh bowl of rice. Optionally garnish with sesame seeds and scallions, and serve with greens.