Mix all ingredients for the pie crust with a dough mixer or by hand into a smooth dough. Wrap it in clingfilm and let it rest for 2 hours.

Degas the dough and fold it like an envelope. Wrap in clingfilm again an let it rest in the refrigerator for at least 2 hours, preferably longer.

Lightly flour your working surface and roll out the dough to a thickness of about 2-3 mm. Fold up the sides. Cover the dough with cling film an let it proof for at least 2 hours in room temperature.

Preheat the oven to 470ºF / 200ºC. Brown butter and add sour cream and mix well. Let it boil for a couple of minutes and remove from heat.

Sprinkle the sugar over the pie crust and spread the topping evenly. Bake the pies for 15 to 20 minutes or until they are golden brown. Let them cool before serving.