Preheat your oven to 400°F. Line a baking sheet with parchment paper or aluminum foil.

In a large mixing bowl, combine the ground beef, ground pork, egg, scallions, sesame oil, garlic, breadcrumbs, ginger, and salt using clean hands.

Roll the meat mixture into 1-1/2-inch meatballs, approximately 18. Place them on the lined sheet pan.

Place the pan in the oven and bake 12 to 15 minutes until the meatballs are browned and the internal temperature reads 165°F when checked with a digital meat thermometer. Prepare the hoisin glaze while the meatballs are cooking.

In a small mixing bowl, whisk together the hoisin sauce, vinegar, soy sauce, sesame oil, garlic, and ginger until well combined. Set aside for the flavors to marry.

As soon as the meatballs come out of the oven, transfer them to a serving platter and coat them with the hoisin glaze while still warm. Sprinkle the scallions and sesame seeds over the top of the glazed meatballs. Serve with forked toothpicks or small forks and plenty of napkins.