Wash the plums, cut them in half and remove the stones. Place them in a saucepan. Cover with water. Drizzle with honey or sprinkle with erythritol and season with cinnamon.
Cook until completely soft, then place in a blender and blend until smooth.
Pour it back into the pot and add cream. Bring to a boil, and it's ready.
Cool completely.
Serve cold. Grate dark chocolate over it when serving.