Evenly spread the remaining mincemeat over the top to cover the marzipan. Roll out the reserved pastry and, using star cutters, stamp out enough stars to decorate the top of the tart (about 14).
Arrange the plums on top of the sugar, cut-side down. Roll out the marzipan thinly to a round slightly smaller than the tin and place on top of the plums. Roll out the pastry just a little bit ...