Set the oven rack in the middle of the oven; preheat to 425 degrees F. Place the raspberries, sugar, flour and lemon juice in a bowl and toss to combine (don’t worry if you crush some of the berries). Let stand for 15 minutes. Brush the bottom pie shell all over with some of the beaten egg to provide a seal between the filling and the crust. Spoon and spread the berries into the pie shell and top with the butter pieces. Brush the edges of the pie with beaten egg. Set on the top crust and crimp the edges to seal. Brush the top of the pie with remaining beaten egg and sprinkle with 1 tsp. granulated sugar. Cut a small whole in the centre of the pie to allow steam to escape. Bake the pie for 10 minutes. Reduce the heat to 350 degrees F and bake until golden brown, about 35 to 40 minutes more.