Bring the mirabelle plums to the boil and then strain them with a grinder or strain them through a sieve. There are about 500g of juice left. Put this juice together with the multivitamin juice and lemon juice in a saucepan and cook to jelly with the preserving sugar according to the instructions on the package.
Immediately fill into boiled jars, close and place on the lid for about 10 minutes, then turn over and let cool (the lid of the jars should be pulled in so that they are tight)
Depending on the size of the jam jars, you can get 3-4 jars out (approx. 400 ml each)