In a large nonstick skillet, heat olive oil over medium heat and add onions and garlic. Sauté until onions are translucent, about 4-5 minutes. Add celery and parsley and cook until soft, about 3-4 more minutes. Set aside to cool.

In a large bowl, combine beef, turkey, egg, onion mixture, breadcrumbs, 0.125 teaspoon salt, pepper and allspice. Mix well and form into 16 meatballs.

Add beef broth to the pan and bring to a boil. Reduce the heat to medium-low and slowly drop meatballs into the broth. Cover and cook about 20 minutes, until cooked through.

Remove the meatballs with a slotted spoon and set aside in a serving dish. Strain the broth, transfer to a blender with cream cheese and blend until smooth. Return to the skillet with the meatballs and simmer.