Peel the apples, remove the casing and cut very small. Drizzle with lemon juice to prevent the flesh from darkening. Stone the mirabelle plums. Put both types of fruit in a large saucepan and mix with the preserving sugar, cinnamon and vanilla sugar and leave to stand for 2 hours.
Then add the apple juice and heat everything. After about 1 minute, take it off the heat for a moment and puree. Then continue cooking until the jam starts to gel. This should be the case after about 4-5 minutes.
Pour into hot rinsed and well dried glasses. Rub the lid and the rim with rum. This way, the jam will last a long time and mold etc. will not stand a chance. After filling and sealing, the jars can be turned upside down for a moment.