Pre-heat the oven to 180˚C.
Combine crust ingredients, either by hand; cutting the yoghurt and butter into the flour, or in a food processor all together.
Rest in fridge for 20mins
Melt the butter, and add the sugar to caramelise.
Add the apples, coating with the butter/sugar mix, cook until golden in colour.
Grease a pie plate, roll out and line the pie plate with the pastry, save the off-cuts for latticing.
Place the pie filling in the pastry case.
Cut lines of pastry and criss-cross across the pie top.