Kram is a word that means a hug, so we rule that one out. There is a word krăm pronounced somewhat the same way. It means something of creamy concistency, it may be a whipped cream with or without fruit or other taste added, it may be any fruit puree thickened with potatoflour or other starch -
Does your mother remember anything more? Is she sure plums was one of the ingredients - could it have been prunes?
Some parts of Scandinavia prune - cream was a holiday dessert:
I don't really have a recipe - you do it just "on feel".

Soak prunes,or use plums
Boil them in water to cover, and some more
They should be tender, but not dissolved
Add sugar to taste
Thicken with a spoon or two of potatoflour stirred in some cold water - Just thicken, don't boil any more.
Pour in a serving bowl, drizzle a little sugar on top to prevent tha forming of skin.
Cool.
Serve with half and half or vanilla custard

You can try this. It may not be what she mean, but you had a cheap, easy and good dessert, and if it isn't what she remember, you have something to start new detective-work from.