Pulverize 200g ginger biscuits in a food processor and mix with 60g melted butter. Press into a 23cm loose-bottomed tart dish
and bake in a 170°C oven for 8 minutes. Remove and cool. For the filling, combine 120g sugar, 3 Tbs cornflour, 250 ml milk,
3 beaten egg yolks and the grated rind and juice from 2 large oranges. Heat in a saucepan over a medium heat, stirring constantly,
until thick, then add 60g butter and stir until melted. Cool for 15 minutes, then stir in 300g sour cream. Pour into the pie crust
and chill for at least 3 hours. Decorate with whipped cream.