1. Preheat the oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish and set aside.

2. Bring a large pot of salted water to a boil. Cook the egg noodles just shy of al dente according to package directions. Drain well, toss with 1 tablespoon butter to prevent sticking, and spread the noodles evenly in the prepared baking dish.

3. In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, egg, half of the minced onion, 2 cloves of the minced garlic, 1 teaspoon kosher salt, 0.5 teaspoon black pepper, and the allspice if using. Gently mix until just combined without overworking the meat.

4. Roll the meat mixture into small meatballs about 1 to 1.25 inches in diameter and place them on a plate or tray.

5. Heat the olive oil in a large skillet over medium-high heat. Working in batches, add the meatballs and brown them on all sides, turning as needed, for about 6 to 8 minutes total. They do not need to cook through at this stage. Transfer browned meatballs to a clean plate and set aside.

6. Reduce the heat to medium. In the same skillet, melt the 4 tablespoons butter. Add the remaining minced onion and cook for 2 to 3 minutes until softened and translucent. Stir in the remaining minced garlic and cook for 30 seconds until fragrant.

7. Sprinkle the flour over the onion mixture and whisk constantly for 1 to 2 minutes until the roux turns lightly golden and smells nutty.

8. Slowly pour in the beef broth while whisking, breaking up any lumps and scraping the browned bits from the bottom of the pan. Continue cooking, whisking often, until the sauce thickens slightly and gently bubbles.

9. Turn the heat to low and whisk in the sour cream, Worcestershire sauce, and Dijon mustard until smooth and creamy. Season with 0.75 teaspoon kosher salt and 0.5 teaspoon black pepper, or to taste.

10. Stir in 0.5 cup of the grated Parmesan cheese until melted into the sauce, then remove the skillet from the heat.

11. Pour about two-thirds of the creamy gravy over the noodles in the baking dish and toss gently so the noodles are evenly coated and well distributed.

12. Nestle the browned meatballs evenly over the saucy noodles. Spoon the remaining gravy over the top of the meatballs and noodles, leaving some of the meatballs peeking through.

13. Sprinkle the remaining 0.5 cup Parmesan cheese over the casserole, followed by 2 tablespoons chopped fresh parsley.

14. Cover the baking dish loosely with foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes, or until the sauce is bubbling around the edges and the meatballs are cooked through to 165°F (74°C).

15. Let the Swedish Meatball Noodle Bake rest for 5 to 10 minutes before serving so the sauce can thicken slightly. Garnish with extra fresh parsley and serve hot with your favorite sides.