Many versions, i.e. every country seems to do it, with ingredients usually found in their other dishes. For me it is simply seasoned ground pork. How it is seasoned...a Chinese version would be ground pork, shiitake mushrooms, other fillings and the seasonings. (This can be whatever you find appealing) I highly recommend Napa or Savoy cabbage, cooked in boiling water till they are pliable. Depending on the size of the leaf, 2oz of filling is usually enough. Steam long enough for the filling to cook, 20 minutes is usually plenty of time. My mom would make more of a eastern European version that would be half lamb, and she would cook in an electric skillet with spiced stewed tomatoes and then add a dollop of sour cream at presentation.