Preheat oven to 200ºC (180ºC fan assisted)/400ºF/Gas 6.
Roll out pastry and use to line flan tin. Put to chill in the refrigerator whilst making the filling.
Grate the rind from the oranges and reserve. Then using a sharp knife remove all pith and skin, and cut each into 4 pieces. Place the fruit in a food processor with the crème fraiche, eggs and sugar and whiz together until blended, and then stir in the grated rind.
Place dates and nuts in base of flan case, add the orange and cream mixture and bake for 25-30 minutes until the set.
Serve warm or cold with whipped cream and fresh orange segments or slices if desired.