1) Using a sharp thin-blade knife, slice marrow and then mash it to measure to 1/2 cup.
2) Take a small bowl and mix beef in it with rest of the ingredients.
3) Shape the mixture lightly into marble-size balls.
4) Place the dumplings in a shallow pan and keep in refrigerator to chill for at least 1 hour to help the dumplings hold their shape better.
5) Cover and cook for 5 minutes, on top of hot beef mixture.