To peel or not to peel, that was the big question. Some recipes say Yes, others say No. Haven't really found a reason one way or the other. These peels were not bitter (like those of pêches de vigne often are), so I left them on. Except for the ones that decided to peel themselves as I pitted and chunked.
All the peaches, halved, pitted, and chunked came to a good 5 cups. I zapped these in a food processor, along with about a tablespoon of lemon juice. A lot of the peel didn't really blend up, so I strained the pulp, ending up with about 3 cups of good pulp and a cup of peel and other bits. (This actually tastes pretty good, but isn't the best texture. Maybe I'll make some peach skin bread or something else.) I've put the pulp, with 1/4 cup sucre de canne, in the crockpot on High. This will cook about 3 hours. Then I'll taste for sugar, add some spices (1 tsp cinnamon, 1/2 tsp ground ginger, 1/2 tsp ground allspice, and a bit of lemon juice*), and let it go overnight on Low, with the lid ajar to lose the moisture.
And that wasn't long enough. Turned the heat to High, lid still ajar, and cooked quite a while longer until it was finally thick enough, only about 1 cup remaining.
Quite tasty, but I can't say that the crockpot method is any better than the way I do apple butter, stirring on the stovetop.
Fruit butters seem to be an American thing, not known in Europe or the UK. It seems they were "invented" to use up fruit that wasn't good enough for jam or jelly or other preserves. I like making my own because I can control the amount of sugar. US products and recipes are generally too sweet for us.
During the summer fruit season, I should try other fruit butters. Apples are available all year round, so it's a shame to stick to that.
* Should have been more than just a "bit" of lemon juice. Ed thought it needed more tartness. Think about how much cider vinegar is used for apple-plum butter and add something similar here.