In a large bowl, stir together the blueberries, blackberries, raspberries (make sure to save some for the 'fingers'), lemon zest, lemon juice, cinnamon, vanilla, salt, cornstarch, and sugar. Pour the berry filling evenly into a deep-dish pie crust. Dot the top of the blueberries with the softened butter. Set aside.
Cut top piece into long strips. Create a lattice, saving enough for 'fingers. Create random lattice pattern and then attach fingers with water. Beat egg with a fork and brush the crust, both rim and lattice. Attach a raspberry to the end of each 'finger.'
Place the pie onto a baking sheet and bake in a preheated oven for (approximately) 60 minutes, or until the juices ooze slightly, and the outer pie crust is golden in color. *Note - if the outer pie crust turns golden too quickly, cover the outer rim of the pie crust with foil. Cool on a cooling rack.
Serve chilled or at room temperature. Top with ice cream or whipping cream if desired.