Unroll the pastry onto a sheet of grease-proof paper, and cut a 1/2 inch border around the edge.
Roll the marzipan out and place inside the border.
Slice plums and arrange the slices in a few lines down the length of the marzipan.
Gently melt the grape jam in a medium saucepan, and dole out over the plums.
At this point the dessert can be kept in the refrigerator 2-3 hours and baked just before you are ready to eat.

1 sheet ready roll puff pastry
150 gram marzipan
2 plums
3 tablespoon grape jam