Wash quinces thoroughly and cut them into small pieces with the core. Put them into a pot with 1.5 litres of water. Cover and simmer for about 1 hour. Put the quinces on a large sieve covered with a gauze cloth and let them drain overnight. Measure out 1 litre of juice. Mix juice and jam sugar well in a large pot.
Bring to the boil over a high heat, stir constantly and let it boil for 3-4 minutes until it becomes bubbly. Place prepared glasses on a damp cloth. Stir the vanilla aroma into the boiling jelly. Immediately fill the jelly into the glasses, close them, place them on the lid and leave them to stand for 5 minutes. Turn over again and let cool off
Waiting time approx. 12 hours