Hi,
In
Fading Feast by Ray Sokolov, of the Wall Street Journal, he has an article on Persimmons from Indiana with recipes. One recipe is for Persimmon Fudge. I am 90% sure where this book is, I bumped into it recently, so I will provide a recipe ... or try google!
In his article, he said there are myths about the ripeness of the persimmon relying on frost. If I recall correctly, he conducted a little experiment where he allowed persimmons to ripen (maybe in a paper bag) without benefit of frost. He had lovely tasting persimmons. I strongly suspect the persimmons you have are under ripe and simply need more time.
I have in my freezer, a treasure chest of goodies, some persimmon puree I made 1-2 years ago when someone suddenly gifted me with more than I could handle. I made some persimmon pies before freezing the rest. You can also make persimmon ice cream.
However, since I reread
Fading Feast recently while doing research on pies, I must admit I am very intrigued by the fudge.
Regards,