1.Peel, core and slice pears in eighths; place in a large pan with the water. Cook, loosely covered, over medium heat, stirring occasionally, for about 10 minutes or until pears are just tender. Drain pears over a bowl, reserve cooking liquid. Cool.
2.To make pastry, process the flour, icing sugar and butter until crumbly. Add the egg yolks and enough water to process until the ingredients just come together. Knead gently on a floured surface until smooth. Cover, refrigerate for 30 minutes. Roll two-thirds of the dough between sheets of baking paper until large enough to line a 20cm pie dish (base measurement). Lift the pastry into pie dish and gently smooth over base and sides to remove any air pockets. Trim edge, freeze for 10 minutes.
3.Preheat oven to moderate (180°C/160°C fan-forced). Cover pastry with baking paper and dried beans or rice. Place the dish on a baking tray. Bake in a moderate oven for 20 minutes, then remove paper and beans. Bake for a further 10 minutes or until base is browned lightly and cooked through.
4.Combine drained pears, flour and caster sugar in a large bowl, stir in blackberries. Stand mixture in a colander over a bowl for 5 minutes to drain well. Spoon filling into the pastry case. Roll out remaining pastry until large enough to cover pie; place over filling. Press the edges together, trim with knife; decorate top with pastry scraps.
5.Brush pastry lightly with some of the pear cooking liquid. Sprinkle with demerara sugar, bake on the lowest shelf for about 30 minutes or until browned (cover the edges of the pastry with foil if the pie is over-browning).
Suitable to freeze. Not suitable to microwave.Note