Blanch the prosciutto bone and rind in boiling water for 5 minutes. Remove the bone and discard the water. Scrape any excess fat from the rind with a sharp knife, then cut rind into narrow strips.

Place the stock in a large pot and bring it to a boil. Add the prosciutto rind and bone, pork shoulder, salami, cheese rind, pepper flakes, onion, carrot, and celery. Let the liquid come to a boil again. Reduce the heat and allow to simmer for 1 hour.

Wash all the greens well. Discard the outer leaves of the cabbage and remove the core. Peel the stems of the broccoli rabe. Remove the center of the escarole leaves and discard. Chop all the greens and reserve.

When the soup has cooked for 1 hour, add the reserved greens and cook for another 30 minutes. Remove the prosciutto bone and rind and the cheese rind.

Ladle the soup into bowls, sprinkle with grated Parmesan and serve.