Instead of ground beef, you can also use a mixture of half ground pork and half ground beef. Sometimes we use ground turkey for the filling. If you're not a fan of raw onion, saute onion in butter first for 5 to 7 minutes on medium heat.
The meat filling can also be made by processing filling ingredients through a meat grinder but do not use a blender or food processor unless you have a special setting for meat.
Pelmeni can also be fried in a skillet. Melt butter or bacon grease in a skillet and saute frozen pelmeni until they are soft and the meat is cooked through, just like pierogi. Pelmeni is usually served with sour cream or vinegar.