Place pork rind, salt pork, ham bone, and onion in a  large, heavy-bottomed pot.  

Cook over medium heat, stirring  frequently, until pork rind is rendered, about 20 minutes.  

 Add beans and enough water to cover by  1⁄2" (about 8 cups).  

 Bring to a simmer, then reduce heat to  low and cook until beans are just tender, about 50 minutes  until they’re just al dente. 

How do you tell  if the beans are done?The skins go papery and begin to collapse and the  cooking liquid is milky.

Then and only then season with salt.  To do so before this would make bean skins rubbery

Set beans aside to cool  Discard onion, bouguet, and bone and aggressively reduce stock or liquor until the proper salinity to taste is established and reserve for the later baking of these beans in cassoulet      

Reserve salt pork piece for inclusion in cassoulet  

Can be prepared 3 days in  advance if it facilitates