You certainly do not need to use a combination of ground lamb and ground beef but I do find the two meats strike a wonderful balance in flavor. If you love the flavor of lamb you can use all lamb. You can also use ground pork if you aren't keen on beef. If you want an all-beef meatball, check out my u003ca href=u0022http://zestful-kitchen.com/korean-meatballs-recipe/u0022u003eKorean Meatballs with Gochujang Drizzle Sauceu003c/au003e.