When I harvested the garden plums I had in mind to try one recipe of simmered plum from my Shojin cuisine book. So I kept 6 of the largest and greenest plums for that recipe. But busy with other things I didn't prepare them right away and the plum have turned from green to a beautiful orange, and were ripening very quickly. So I decided to go for an other manner to cook them, simply preparing some kind of compote. I put the plums in ample water and boiled them at low heat for 2h under cover; then I drained most of the water and kept only 5 to 10mm in the pan, added 2tbs of brown sugar and simmered at low heat again for 30min without cover, or until almost all the syrup is gone. Instead I obtained a thick jelly (the brown paste in between the plum on the picture).
You can serve the plums warm, at room temperature or cold.