Preheat oven to 190C/375F/gas 5. To make the pastry, pulse flours, salt and cold butter together in a food processor for 30 secs until combined and resembling uneven sized breadcrumbs. Add beaten egg and blitz until the dough just comes together (add a drop of cold water if needed). Shape into a ball, flatten slightly and wrap in cling film, then chill in the fridge for 30 mins.

Roll out the pastry on a lightly floured surface and press gently into a greased 9 inch (23cm) tart or pie tin. Prick the base lightly all over with a fork. Line with tin foil or greaseproof paper and pour in baking beans or uncooked rice and blind bake in the preheated oven for 15 mins, then remove the beans or rice and foil before returning to the oven for another 5 mins. Allow to cool slightly while you make the filling. Reduce the oven temperature to 180/350F/gas 4.

For the filling, whisk all of the ingredients in a large bowl until smooth and thin. Pour into the pastry case and bake in the oven for 45 mins to 1 hour, until the custard is set round the edges and just has a slight wobble in the centre. Allow to cool completely (even better, chill for an hour or two after cooling) before serving with fresh whipped or pouring cream, or even my sugar free ice cream!