1. Remove the leaves and the larger stems, and wash the blackcurrants if necessary.
2. Place in the preserving pan, add 1 litre of the water, and simmer gently until thoroughly tender.
3. Mash well, then strain through a scalded jelly bag, leaving it to drip for at least 15 minutes.
4. Return the pulp left in the jelly bag to the pan, add the rest of the water and simmer for 30 minutes.
5. Strain this pulp through the bag and leave to drip for 1 hour.
6. Mix the 2 extracts together.
7. Measure the extract, return it to the cleaned pan, and bring to the boil.
8. Add 800g sugar for each litre of extract and stir until dissolved.
9. Boil steadily, without stirring, until setting point is reached.
10. Remove from the heat, skim, pot, cover, and label.