@shrinkrap, I’m sure you’ve heard of this recipe before, The NYT original Plum Torte recipe by Marian Burros. Very easy and quick, so delicious. Visually more appealing with red or purple plums, but I’ve made it with the Green Gage, and it’s still really good.
Also, when jamming in the summer, I often mix plums half and half with strawberries and raspberries. In both cases, the berries dominate, with a nice, tart, plum undernote. I’ve mixed with blackberries as well, and while still good, I didn’t really get the blackberry flavor I was hoping for.