In a large bowl, combine ground beef, ground pork, panko breadcrumbs, egg yolks, green onions, chopped parsley, ground allspice, nutmeg, kosher salt, and freshly ground black pepper. Mix well using your hands until just combined. Shape the mixture into 24 meatballs, each about 1 to 1.25 inches in diameter. Set aside.

Heat olive oil in a Dutch oven over medium-high heat. Add the meatballs in batches and sear for about 2-3 minutes on each side until browned. Remove from the pot and set aside.

In a separate pot, bring salted water to a rolling boil. Add the elbow macaroni and cook according to package directions, about 8-10 minutes until al dente. Drain and set aside.

In the same Dutch oven, melt the unsalted butter over medium heat. Whisk in the flour until lightly browned. Gradually add beef stock while whisking until the mixture thickens, about 3-5 minutes.

Return the meatballs to the creamy sauce and stir gently to coat. Heat through for about 5 minutes. Stir in the cooked elbow macaroni and sour cream until well combined, about 2-3 minutes. Adjust seasoning if necessary.

Spoon the creamy Swedish Meatball Pasta onto plates. Garnish with extra chopped parsley and serve hot.