Start by making the crust. Whisk the flour, sugar and salt in a medium sized bowl. Transfer the flour mixture into a food processor and add the butter and shortening. Pulse the food processor until the butter and shortening have been cut into the flour and the flour is crumbly. Add the egg yolk and lemon juice and process until combined. With the food processor still going, stream the water and milk in through the feed chute. Process until the dough has come together and has balled up on one side of the processor. Once the dough has come together, divide into two discs and wrap with plastic wrap. Place the discs into the fridge to chill for 1 hour.
While the dough is chilling, make the filling. Whisk all of the ingredients except the cornstarch in a large bowl. Once combined, add the cornstarch and mix until incorporated. Set aside.
Once the pie dough has chilled, preheat the oven to 350 F. Spray a 9” pie pan with baking spray. Unwrap one dough disc and place between two sheets of parchment paper that have been lightly dusted with flour. Use a rolling pin to roll the disc out into a rough 12” circle about ¼” thick. Carefully roll the dough around the roll pin to make it easy for transferring. Unroll the dough over the pie pan. Press the crust into the bottom and sides of the pie pan. Fold the excess dough around the top edge under just the top edge so that it is thicker then crimp the edges. Use a sharp knife to remove any excess dough from around the top edge of the pan. Use a fork to poke holes into the bottom of the crust. Pour the filling into the crust and spread to the edges.
To make the top crust, roll out in the same manner as the bottom crust. Use various sized star cookie cutters to cut out as many stars from the dough sheet as possible. Place the larger stars onto the pie first then follow with the smaller stars. Cover at least 75% of the filling surface.
To make the egg wash, whisk all ingredients together in a small bowl. Use a pastry brush to brush the egg wash onto the surface of the top crust. Sprinkle it with turbinado sugar. Place the pie into the oven to bake for 55 minutes or until golden brown and baked through. You may need to cover the edge crust with tin foil halfway through baking to prevent it from browning too much. Once baked, remove from the oven and let cool for 20 minutes before serving.