The above ingredients make about 1.5 liters of jam.
Wash and drain the cornels. Cook in a saucepan with 500 ml water over low heat for about 5-7 minutes until soft. Pass the fruit and cooking liquid through a large-mesh sieve and allow to cool.
Mix 1 kg of fruit pulp with the preserving sugar in a large saucepan. Halve the vanilla pod lengthways, scrape out the pulp, add to the fruit. Bring to the boil over high heat while stirring until everything is bubbly. Let it simmer for 4 minutes, stirring constantly. Quickly fill the twist-off jars to the brim with the mixture and close them immediately.