Gently heat the cranberries, sugar and crème de cassis in a saucepan 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 set over a saucepan of barely simmering water, making sure the water does not touch the base of the bowl. Stir in the fromage frais and vanilla extract and beat together well. Cover and chill.
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.