For the vanilla liqueur, slit the vanilla beans lengthwise, scrape out the pulp and bring both to the boil with water and 50 g sugar and simmer for 10 minutes while stirring.
After cooling, strain through a kitchen towel. Pour the mixture into cold-rinsed preserving jars or bottles, top with rock candy and gin.
Put the vanilla beans back in and let it work for about 2 months tightly closed before consumption.