Line a rimmed baking sheet with heavy-duty foil and lightly spray it with cooking oil. Preheat oven to 400℉/204℃.

Combine all your meatball ingredients in a large mixing bowl: ground beef, ground pork, onion, garlic, parsley, breadcrumbs, parmesan cheese, milk, egg, Worcestershire sauce, pepper flakes, salt, and pepper. Thoroughly mix using a wooden spoon or your clean hands until fully combined.

Shape the meat mixture into 1½ to 2-inch meatballs (about 20-24 balls) and arrange them on the prepared baking sheet in a single layer. Bake for 15-18 minutes or until browned, but they don't need to be cooked through at this point. Remove from the oven and set aside.

While meatballs are baking, heat oil on medium-high heat in a large saucepan. Add chopped onions and garlic, and saute for 2-3 minutes until translucent.

Next, add barbecue sauce, ketchup, and brown sugar. Mix well, then add paprika, Italian seasoning, chili powder, Worcestershire sauce, and beef broth.

Stir and bring to a boil. Reduce the heat and simmer for 10-15 minutes, stirring frequently. Adjust seasonings to taste.

Add cooked meatballs to the skillet with the barbecue sauce and gently coat meatballs with the sauce; continue simmering for 3-4 minutes until the sauce is slightly thickened.

Garnish with green onion and serve over rice, mashed potatoes, or desired side.