Place the ground meat in a mixing bowl. Add the chopped onion, minced garlic, rock salt, 1 teaspoon of soy sauce and 1/3 teaspoon of grated ginger. Mix just until combined. Form into balls (how large or how small is up to you) then cook either by deep frying, pan frying, baking, grilling or broiling.
When the meatballs are almost done, make the teriyaki sauce. Pour the quarter cup of soy sauce, mirin, honey and half teaspoon of grated ginger is a shallow pan and heat until simmering. Add the meatballs and cook over medium-low heat until the meatballs soak up the sauce and acquire its color. For even coloring, roll the meatballs around in the sauce while simmering.
To serve: If any sauce is left, spoon over the meatballs. Sprinkle with toasted sesame seeds and sliced scallions before serving.
Serve the meatballs hot.