In a large mixing bowl, combine the ground beef, ground pork, egg, panko breadcrumbs, salt, garlic powder, onion powder, allspice, nutmeg, and pepper. Mix until just combined.

With clean, damp hands, roll the mixture into 1¼ to 1½-inch meatballs, aiming for about 25-30 in total.

In a large skillet, heat olive oil over medium-high heat. Add meatballs in batches and cook for 5-7 minutes until evenly browned.

Remove the meatballs from the skillet and set them aside, keeping the browned bits in the pan.

Reduce heat to medium, add butter to the skillet, and whisk in the flour to create a roux, cooking for 2 minutes.

Gradually whisk in beef broth, then add Dijon mustard and Worcestershire sauce. Simmer for 3-5 minutes until thickened.

Return meatballs to skillet, cook for another 10 minutes until heated through and internal temperature reaches 165°F.

Stir in sour cream and adjust seasoning with salt and pepper before serving.