- Make a zest of lemon peel, whisk egg with 1 tsp water. Set aside.
- Heat oven to 425*F. Roll out your crust on a well floured surface, fold it in half.
- Combine sugar, cornstarch and lemon zest in a large bowl. Add blueberries and mix finely. Spoon into pie plate. Roll remaining pastry into a circle, make it's 9 strips. Completely cover pie in lattice pattern over fruits. Lightly press the edges of a crust together to seal, brush pastry with egg mixture. Bake at least 15 minutes.
- Reduce oven to 375*F. Bake for 30 minutes further so that the pastry becomes flaky and nicely glazed and fruit is bubbling; cool it, sift sugar over top before eating.