Beat butter, sugar and vanilla until foamy. Gradually add the egg yolks.
Mix flour, polenta and salt and into the mixture until everything is well combined.
Form two balls. One approximately 2/3 of the dough and the other approximately 1/3 of the dough. Wrap in plastic wrap and place into the fridge for 30 minutes.
Roll the larger ball between two sheets of baking paper to fit a 25cm springform tin, including a 2cm edge.
Grease the springform tin well and line with the pastry. Roll the smaller ball to about 27cm round sheet. Place both into the fridge for 15 minutes.
Preheat the oven to 180 degrees C.
Remove the baking paper from the larger pastry carefully and lay it into the springform tin. Lift up the edges. Bake for 15 minutes. Remove the tin from the oven and increase the temperature to 200 degrees C.
Drain the peaches and lay them over the pastry case. Spread the blackberries over them. Sprinkle with 3 tablespoons sugar.
Lay the other piece of pastry over the top, carefully removing the baking paper. Beat the egg yolk and milk then brush the pie with it.
Sprinkle with the remaining sugar. Bake in the preheated oven for 45 minutes until the pie is golden brown.
I'm pretty sure it'll be delicious, but I've nearly lost my mind trying to 'carefully remove the baking paper' from the pastry. Having taken it in and out of the fridge, rolling and re-rolling, tried using a cold knife to pry it off intact, now I'm just about ready to throw the whole thing out the window. Any tips? - 09 Nov 2011