Using jam sugar instead of regular sugar to make jam has the advantage that the jam sets in only a few minutes, so the jam has a brighter colour and fresher taste. The plum brandy is added at the end, otherwise it will just evaporate.
Chop plums. In a large bowl or a pot combine plums with jam sugar, cinnamon and cloves. Toss to evenly distribute the sugar and spices. Cover and refrigerate overnight.
The next day, slowly bring to the boil. Remove any foam with a slotted spoon and discard. Cook till the jam sets, which should take only a few minutes. Test a spoonful on a chilled plate, if it is no longer runny, it's done. Stir in the plum brandy.
Have sterilised jars ready. Fill piping hot jam into jars and close immediately with lids.