Wash and peel plums, but do not remove stems (to peel plums more quickly, blanch them for 1 minute in boiling water, drain, and rinse in cold water—the skin will come off easily).
Place the sugar and water in a laminated pot and bring to a boil. Reduce heat to medium and simmer for 10 minutes.
Add the plums and simmer uncovered for 30 to 35 minutes ov