Preheat your oven to 400 degrees. Line a baking sheet with parchment paper, foil or a silicone baking mat and set aside.
In a large bowl, combine the ground beef with all the rest of the ingredients for the meatballs. Using your hands (I like to wear disposable plastic kitchen gloves) or a mixing spoon, mix together until well combined. Roll the mixture into 1¼ to 1½ inch meatballs, forming about 15-18 meatballs. You can also use a cookie scoop if you prefer.
Place the meatballs onto the prepared baking sheet and bake for about 22 to 24 minutes, or until all sides are browned and the meatballs are cooked through. Remove from the oven.
For the hoisin sauce:
Whisk together all of the ingredients in a bowl. Pour the hoisin sauce directly over all of the meatballs and bake in the oven again for another 2 to 3 minutes. Remove from the oven, garnish with finely diced green onions and serve immediately.