Confiture aux Prunes

• 1 kg/2¼ lb very sweet plums, halved and stoned
• 150 g/5

Sprinkle the plums with the sugar and leave to macerate overnight. Next day, put the plums in a saucepan with the vanilla or lemon, if you like, and cook over low heat for about 3 hours, until the temperature reaches 103°–105°C/217°– 221°F and round bubbles form on the surface of the syrup. The jam should still be slightly runny.

Pour the jam into sterilized jars while it is still hot.