Preheat the oven to 200°C
Cut the plums in half and remove the stones
For the frangipane: beat together the softened butter, sugar, ground almonds and the egg yolks
Roll out the puff pastry and use individual tart rings to cut the pastry into discs
Place a pastry disc in the base of each tart ring and then add frangipane, spreading it over the pastry
Arrange the plum halves on top of the frangipane and then transfer to the oven
Bake for 35 minutes then decorate with flaked almonds.