Form your bottom crust into your plate, or use a pre-made crust, and cut out small circles in the top crust portion. Put both crusts in the freezer while you make the filling.

In a large bowl, stir together the blueberries, sugar, cornstarch, salt, lemon zest, juice, and vanilla extract until there are no dry pockets of cornstarch remaining, and the blueberries look like they are coated in a paste. Pour the filling into your bottom crust in the pie plate, and lay the rounds all over the top of the filling. Place the entire pie back in the freezer.

While the pie chills, line a large cookie sheet with foil and place it in your oven. Preheat the oven, with the pan in it, to 400 degrees. Once the oven is preheated, brush the top of your pie with the beaten egg generously. Sprinkle the coarse sugar all over the top, and then carefully place the pie in the oven on the preheated cookie sheet.

Bake the pie for 40-45 minutes, or until the top is deeply golden brown all over and the filling is bubbling. Cool the pie completely before slicing and serving, optionally with whipped cream. Enjoy!