Place all meatballs ingredients, except for onion and garlic, in a medium-sized bowl.
In a food processor or immersion blender cup, chop onion and garlic until fine. If you don't have this equipment, chop very finely with a knife. Add to the meatball mixture.
Mix until just combined (don't overmix--the meatball will be tough). Form into 24 balls, about one heaping tablespoon each. You could use a cookie scoop and place them on a cookie sheet, or use a mini muffin tin sprayed generously with cooking spray to portion them out.
Broil meatballs for 10 minutes.
While meatballs cook, add all teriyaki sauce ingredients to the same food processor or immersion blender cup. Blend until smooth.