Begin by blind-baking the pie crust. Blind baking is important in making any pie because it involves baking the crust initially on its own, allowing for the final product to have a crispier bottom crust, not gooey and still uncooked). To blind bake, grease a glass pie plate and set down the bottom pie crust. Starting from the middle and working your way out, pat down the crust so it lies flat on the plate. Using your fingertips, ruffle the edges to make it look pretty.
Use a fork to make 15-20 indentations in the bottom of the crust (this allows air to escape from the crust and prevents bubbles from forming). Now grease the inside of the crust and line it with a piece of aluminum foil.
Next, pour in dried rice or beans to line the aluminum foil. Bake for 10 minutes, then remove aluminum and rice and allow the crust to cool slightly while you prepare your filling.
In a large bowl, combine the strawberries with sugar, lemon juice, vanilla extract, cornstarch, and salt.
In a smaller bowl bowl, combine the blueberries with sugar, lemon juice, cornstarch, and salt.
Fold a piece of aluminum foil at a 90° angle to act as a barrier between your blueberries and strawberries. Pour the blueberries into the smaller wedge and the strawberries into the larger wedge. Carefully remove the aluminum and adjust the berries as needed.
Roll out your second pie crust. Using a pizza cutter and a ruler, cut three full length 1″ stripes and two half length 1″ stripes into your dough. Use the remaining dough to cut your stars (I used a sharp knife). Place the stars and stripes as seen in the picture, being sure to press the ends of the stripes into the blind-baked crust.
Brush the entire crust with whole milk, then bake for 40 minutes. Allow to cool completely before eating!