The Purifying Parboil
Place the chunked beef shanks into a large pot and cover completely with cold water. Bring to a rolling boil over high heat. Allow it to boil vigorously for 8 to 10 minutes. Drain the meat entirely through a colander and rinse each piece thoroughly under cold running water to remove any residual gray film. Wash out the pot completely.
Starting in cold water draws out blood clots and surface proteins from deep within the bone and muscle structure, ensuring your final broth is brilliantly clear, pure, and free of bitter off-flavors.
The water will turn muddy and thick with gray foam, while the beef chunks will shrink slightly and tighten.