Mix flour and salt in a bowl. Cut in shortening using a pastry cutter. Cut in butter.
Add oil and milk and stir until a soft dough forms.
Cut dough in half. Wrap one half in plastic wrap and set aside.
Roll the other half and place into a pie pan.
Toss blueberries in lemon juice, sugar and corn starch. Pour into pie crust.
Roll out second pie crust and place on top. If you'd like a lattice top, cut the pie crust into 10 strips. Place 5 strips across the pie. Weave the other 5 strips in the opposite direction to create a lattice. See video for visual.
Cut off excess pie crust using a knife and crimp/pinch the edges.
Cut 3-4 slits in pie crust for venting unless you made a lattice crust. No venting necessary for lattice pie.
Mix egg and water together. Brush over pie crust. Sprinkle top of pie with sugar.
Bake 55 minutes at 425 degrees or until crust is golden brown and juice begins to bubble through slits in crust. Cool on cooling rack at least 2 hours to allow blueberry filling to thicken.