Never heard of Black Peanuts before. Here it is common as a southern snack to have boiled peanuts. Typically they are salty and if done properly soft. Not hard to make them.
To make boiled peanuts all you need are green peanuts (haven't been roasted or dried yet) about a cup of salt (varies depending batch size) a large pot with room for excess water, cover peanuts to a water level that won't go over the top of the pot with lid on, raise to boiling temp, and then leave it at a boiling simmer for several hours, adding water when needed. They are ready when the some of the hulls become soft.