Step 1

Pre-heat the oven to 400 degrees. Line a heavy baking sheet with aluminum foil and set aside.

Step 2

Combine the strawberries, blueberries, raspberries, and blackberries in a large mixing bowl. Add the lemon juice and vanilla extract and stir to combine. In a separate small bowl, stir together the sugar, cornstarch, and cinnamon. Add this mixture to the berries and stir until the berries are coated. Let sit for 15-20 minutes.

Step 3

Remove the pie crust (in tin plate) from the freezer and use a pastry brush to brush the entire surface of the frozen pie crust with beaten egg white. You won’t use all the egg white, just discard the rest. Place in the refrigerator for 15 minutes.

Step 4

After the waiting period, place the pie crust (in tin plate) on the foil-lined baking sheet. Spoon the berry mixture evenly into the pie crust.

Step 5

Place the baking sheet with the pie on it into the oven and bake for 30 minutes. Tent a piece of aluminum foil over the top to prevent the edges from getting too dark and return it to the oven for another 25 minutes until the berries are bubbly. Remove from the oven and allow to cool for at least 2-3 hours before slicing. Cut into 8 slices and serve.