MEATBALLS: Heat 1 tablespoon olive oil in a large skillet over medium heat. Add onions, cook, stirring frequently, until onions have become translucent, about 2-3 minutes. Remove from heat.
In a large bowl, combine cooked onions, ground beef, ground pork, bread crumbs, eggs, allspice, and nutmeg; season with salt and pepper. Using a wooden spoon or clean hands, stir until well combined. Roll the mixture into 1 1/4 to 1 1/2-inch meatballs, forming about 40 meatballs.
Add 1 tablespoon olive oil to the skillet. Working in batches, add half of the meatballs, cook until all sides are browned, about 4-5 minutes; transfer to a paper towel-lined plate. Repeat with remaining meatballs.
SOUR CREAM SAUCE: Melt butter in the skillet. Whisk in flour until lightly browned, about 1 minute. Gradually whisk in beef broth, cook, whisking constantly, until slightly thickened, about 1-2 minutes. Stir in sour cream; season with salt and pepper and 1 tablespoon parsley.
Stir in meatballs and cook, stirring occasionally, until heated through and thickened, about 5-8 minutes.
Meanwhile, cook wide egg noodles as directed on package and drain.
Serve meatballs with sauce over wide egg noodles garnished with remaining parsley.