As it turns out, no one was remotely underestimating the toughness of quinces when they said they were rock hard and you really had to work on and cook them. It was a fair workout to get them cubed. Anyway, once peeling and cubing them (got about 2 c), I tossed them in a saucepan with some water (1/2 c) and sugar (1/3 c) and got them cooking over medium-high heat. Once that was going, I added 1/4 c crystallized ginger, four large rounds of fresh ginger, and just under 2 cups of peeled and cubed persimmon. I boiled this all together until the quince finally softened enough so that I could mash it a bit. The mixture was good but sweet so I added a couple grinds of white pepper. The result is actually a lovely sauce/jam that I could see being great on cream cheese and bagels, crackers and a sharp cheese, or even a glaze for pork or chicken. I'll keep you posted but am pleasantly surprised by this creation. It's pretty, too.