In a large mixing bowl, combine chopped yellow onion, panko breadcrumbs, large eggs, salt, ground allspice, ground nutmeg, and black pepper.
Gently stir in 80/20 ground beef and ground pork until just combined. Do not overmix.
Roll the meat mixture into 1½ inch meatballs. Place the meatballs on a baking sheet or plate and refrigerate for 15 to 20 minutes.
Heat olive oil in a large skillet over medium-high heat.
Brown the meatballs in batches for about 1 minute per side until browned on the outside. Remove the meatballs from the skillet and set aside.
In the same skillet, melt butter. Use a spatula to scrape the browned bits from the bottom of the pan.
Whisk in all-purpose flour and cook for 2 to 3 minutes, whisking continuously until lightly browned.
Slowly whisk in beef broth and bring the sauce to a low simmer.
Whisk in Worcestershire sauce, salt, and black pepper.
Place ½ cup sour cream in a small bowl. Spoon some of the warm sauce into the sour cream and stir until smooth. Stir the sour cream mixture back into the skillet and cook over low heat until fully incorporated.
Return the meatballs to the skillet and spoon the sauce over them. Cover and cook on low heat for 10 to 15 minutes until the meatballs are fully cooked through.
Serve warm topped with fresh chopped parsley if desired.
Video
Notes
These meatballs are great served as is, over mashed potatoes or egg noodles. I find it’s best to stir in the ground beef and pork into the meatball mixture with your hands to ensure that the seasonings are evenly distributed.You can use a wooden spoon but in my experience, hands work best. You can prepare the meatballs the night before cooking if you prefer. Make sure to refrigerate them covered so that they do not dry out. It’s important to mix some of the sauce from the pan with the sour cream before adding it to the pan so that the sour cream does not curdle and blends well into the sauce. You can use 1 cup of heavy cream instead of the sour cream if you prefer. Use an instant read meat thermometer to make sure that the meatballs are cooked to a safe temperature of 165 degrees F.