The secret to broth balls is getting the right amount of liquid in with your meat. I boil a pound of frozen meat in two cups of water. By the time the meat is cooked there is about a cup and a half of water leftover (but now it's meat stock - don't throw it out!). I puree all of this in the Vitamix. Let it chill in the refrigerator, and voila! You may find that you need to adjust the amount of water based on fresh vs. frozen meat. Your finished mixture should be quite liquidy before going into the refrigerator. If it doesn't gel after refrigeration you can add in some gelatin.
Note that these must be served cold or at room temperature. If they are heated they will melt and turn to mush.