Heat 1 tablespoon olive oil in a large pan over medium heat. Add onion, and cook, stirring frequently, until onions have become translucent, about 5-6 minutes; set aside.
In a large bowl, combine ground beef, ground pork, egg yolks, bread crumbs, nutmeg and onion. Season with salt and pepper. Using a spoon or just your hands, mix until well combined. Form the mixture into 1¼ inch meatballs, creating about 30 meatballs. Add the remaining 1 tablespoon olive oil to the skillet. Add meatballs, in batches of 6, and cook until all sides are browned, about 4-5 minutes. Transfer to a paper towel-lined plate.
To make the gravy, melt butter in a large pan. Whisk in flour until lightly browned, about 1 minute. Gradually whisk in beef broth. Keep whisking constantly until slightly thickened, about 1-2 minutes. Stir in sour cream; season with salt and pepper, to taste. Add in meatballs and cook, stirring occasionally, until heated through, about 10 minutes.
Serve immediately. Place meatballs and a large spoonful of sauce on top of egg noodles. Top it off with a sprinkle of parsley.
Recipe by Big City Tiny Kitchen at https://bigcitytinykitchen.com/swedish-meatballs-egg-noodles/