there are lots of syrup variations. My favorite is Syrope de Liege which is 50% apples, 45% pears, and some dates. Plums can be substituted for the dates, 50/40/10.
Pflaumenmus, a German recipe ("mousse of plums"). 4kg plums, 700g sugar. Shred the plums in a blender, mix with the sugar, then spread the paste onto a high-sided baking tray covered in butter. 1.5h in the oven at 160C. The resulting mass is quite dry and gets spread onto bread or rolls for breakfast.
Good luck!
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