For 4 people
Separate the stems from the rosehips and wash them. Then, boil them in water for about 35 to 40 minutes until tender, then pass them through a sieve to collect the juice and remove the seeds and the black end of each berry.
Blend the recovered flesh with a little of the cooking juices to obtain a smooth purée, then pass through a sieve to remove the last stinging hairs and unwanted seeds. Next, add 70% of the flesh's weight in caster sugar, lemon juice, and a scraped vanilla pod.
Let it cook for 12 to 15 minutes and pour the boiling jam into previously cleaned and dried jars. Seal the jars tightly.