Add 1 tablespoon of butter to cast iron skillet and saute onions until translucent. Remove from flame, set aside and let cool.
Using a medium bowl, mix ground beef, ground pork, egg, salt, pepper, nutmeg, allspice, bread crumbs, and parsley together.
Once onions have cooled a bit, add to meat mixture.
Using a small cookie scoop, about 1- 1½ inch. Scoop out meat mixture, roll until smooth and tight and place onto a plate or baking sheet (the baking sheet is only used to place the meatballs on).
Add oil to skillet, cook half of the meatballs on medium heat until browned on all sides.
Remove browned meatballs from pan and place on a paper towel lined plate. Continue cooking the remaining meatballs, then remove from pan.