Gently heat the cranberries, sugar and crème de cassis in a pan for a few minutes until the cranberries are just softened. Strain the cranberries and set aside to cool, reserving the juice.
Melt the white chocolate in a bowl over a pan of simmering water (see
Add the cranberry jelly to the reserved cranberry juice in the pan. Heat gently to melt the jelly and then stir to combine.
Spoon the vanilla and white chocolate mixture into the pastry cases 1–2 hours before serving. Top with the cranberries and spoon the cranberry syrup over to glaze. Chill until needed.