Start by combining the breadcrumbs, Parmesan cheese, beaten egg, and milk in a large bowl. Stir until the mix feels evenly moist. Then, mix in the onions, garlic, and seasonings like nutmeg, allspice, and oregano to enhance the overall flavor. Finally, add the ground beef and pork, and gently fold everything together. Be careful not to overwork the mixture, as this can make the meatballs tough.

Roll the mixture into 1.5-inch balls, using damp hands or a cookie scoop for uniformity. Place the meatballs on a plate and refrigerate them for 15 minutes. This quick chill does wonders for helping the meatballs hold their shape while cooking.

Heat a drizzle of olive oil in a large skillet over medium heat. Sear the meatballs in batches, letting each side brown evenly. This step not only locks in the juices but also creates flavorful bits in the pan, which we’ll use for the sauce. Once browned, set the meatballs aside on a plate.

Melt butter in the same skillet, scraping up those browned bits for extra flavor. Add flour and whisk until golden, forming a smooth roux. Gradually pour in the beef broth, whisking constantly to avoid lumps. Add Worcestershire sauce, Dijon mustard, and chicken bouillon, then simmer until the sauce thickens slightly into a rich, golden gravy.

Temper the sour cream by stirring a little warm gravy into it, then whisk the mixture back into the skillet. This prevents curdling and ensures the sauce is silky smooth. Add the meatballs back into the skillet, spoon the sauce over them, and simmer for 10–15 minutes until fully cooked. Sprinkle with parsley and serve!