In a large bowl, combine ground beef, ground pork, breadcrumbs, milk, half of the chopped onion, minced garlic, nutmeg, allspice, salt, and pepper. Mix until just combined.
Shape the mixture into small meatballs, about 1 inch in diameter. Set them aside.
Heat a large pot over medium heat and add a splash of oil. Once hot, add the remaining onion and sauté until translucent, about 2-3 minutes.
Carefully add the meatballs to the pot, browning them on all sides for about 5-7 minutes. You may need to do this in batches to avoid overcrowding.
Once the meatballs are browned, pour in the beef broth, bringing it to a gentle boil.
Add the chopped carrots and diced potatoes to the pot. Reduce the heat to a simmer and cook for about 15-20 minutes, or until the vegetables are tender.
Stir in the fresh spinach and heavy cream, allowing it to simmer for an additional 5 minutes.
Adjust seasoning with salt and pepper as needed before serving.
Notes
Ladle the soup into large bowls and finish with a sprinkle of fresh dill on top for a pop of color and flavor. Serve with crusty bread on the side for dipping.