Place the flour, butter and duck fat in the bowl of a food processor and process until it resembles fine breadcrumbs. Duck fat and butter must be chilled to ensure a good result. Add the egg yolk and water then process until dough just starts to form. Do not over process as this will make pastry tough.
Remove dough from processor and lightly knead till smooth on a floured surface. Cover with plastic wrap and place in the fridge to rest for 30 minutes.
Preheat the oven to 160°C. Roll out the pastry on a lightly floured surface and then carefully press it into a 9-inch pie tin. Use a sharp knife to trim the excess. Line the pastry with baking paper and fill with baking weights or rice. Bake in the oven for 20 mins.
Pour your choice of filling mixture into the pastry and then bake in the oven for 50 mins or until it doesn’t jiggle in the middle,