In a skillet over medium heat, warm 2 tablespoons of olive oil. Add 1 finely chopped onion and 2 minced garlic cloves, sautéing until softened and fragrant, about 5 minutes.

In a large mixing bowl, combine ½ cup of breadcrumbs, ¼ cup of grated Parmesan cheese, 1 large egg, and ¼ cup of milk. Add the cooled onion and garlic mixture with ½ teaspoon of nutmeg, salt, and pepper. Mix in 1 pound each of ground beef and ground pork.

Roll the meat mixture into 1½-inch balls, forming about 20 meatballs. Chill in the refrigerator for at least 15 minutes.

In the same skillet over medium-high heat, brown the meatballs in batches for about 1 minute on each side until golden brown.

Melt 2 tablespoons of butter in the same skillet. Stir in 2 tablespoons of flour, cooking for about 2 minutes. Gradually whisk in 2 cups of beef broth and bring to a smooth boil.

Temper ½ cup of sour cream with some gravy, then stir into the sauce. Return the browned meatballs to the skillet and let them simmer for 10-15 minutes until cooked through.