In a food processor, add flour, sugar, xanthan gum and salt. Pulse to combine. Add cold diced butter into food processor and pulse until mixture resembles coarse crumbs.

In a small bowl, add egg, cold water and apple cider vinegar. Use a fork to beat the egg and mix. Pour egg mixture into food processor and pulse a few more times until dough is just moistened.

Transfer the pie dough to a glass bowl and use clean hands to shape it into a ball, slightly flattened. Cover the bowl with plastic wrap and place in the fridge to chill for at least 1 hour.

While dough is chilling, add 1 cup of the strawberries to a food processor and puree. You may also use a fork to mash thoroughly.

In a medium saucepan, whisk together sugar, cornstarch, water and strawberry puree. Bring to a boil over medium heat, stirring constantly. Cook for 3 additional minutes, until the strawberry mixture begins to thicken and turn translucent. Set aside and let cool to room temperature.

Remove chilled pie dough from refrigerator and place on counter for about 15 minutes. Transfer pie dough to a lightly floured piece of parchment paper. Sprinkle a little flour on top of the dough and add an additional piece of parchment paper on top. Roll out the dough with a rolling pin into a 12 inch circle. Transfer the dough to an ungreased pie pan and press into place - flattening the crust against bottom and sides as well as touching up any cracks. Trim off any excess crust and crimp or flute the edges.

Cover the pie shell with a double layer of aluminum foil (including the edges) to prevent burning. Fill the pie with pie weights and blind bake at 375 degrees for about 25-28 minutes. Remove the pie weights and the foil and continue to bake until the crust is a golden brown, about an additional 10 minutes. Remove from oven and allow crust to cool for a minimum of 1 hour before filling.

While the crust cools, hull strawberries and slice in halves or fourths depending on size and place in a large bowl with the fresh blueberries. Add the prepared strawberry glaze and carefully fold with a spatula until the berries are evenly coated. Fill the cooled pie crust with the berry filling, being sure to turn any cut sides to face down. Chill in the fridge for 2 hours until set.

Place heavy whipping cream, powdered sugar and vanilla in an electric mixer. Start mixing on low and then turn setting to high until cream is smooth, thick and doubled in volume. Add whipped cream to a piping bag fitted with a large star pastry tip and pipe onto pie. (Note: fresh whipped cream is best used within 5 hours).

Store pie and whipped cream in the fridge until ready to serve.