1. Wash, halve, and stone the fruit and put it into a preserving pan with the water.
2. If desired, crack a few of the stones, remove and halve the kernels and blanch them by dipping in boiling water.
3. Add the halved kernels to the pan.
4. Simmer until tender and reduced by one-third.
5. Add the sugar and stir over low heat until dissolved.
6. Bring to the boil and boil rapidly until setting point is reached.
7. Remove from the heat, skim, pot, cover, and label.