For the Pie Crust:

1. In a large bowl, mix together the gluten-free flour, salt, and xanthan gum. Using a large cheese grater, grate the butter into the flour.  Using a fork or dough blender, work the dough until crumbly and mealy. Don’t overwork the batter.
2. Evenly sprinkle the ice water in the butter and flour mixture, use a spatula to mix in between adding the cold water. If the batter feels too dry to shape into a ball, add an additional 2- 3 Tablespoons of ice water, and mix until just combined. 
3. Form the dough into a single ball, and flatten it into a disk.
4. Wrap the dough in plastic wrap, and let it chill in the refrigerator for 1 hour up to 3 days.
5. Once the dough has chilled, preheat the oven to 375 degrees Fahrenheit. Remove the dough from the refrigerator and allow the dough to rest at room temperature for 10 to 15 minutes before rolling.
6. On a lightly floured surface, sprinkle a little flour on top of the dough and roll between two pieces of plastic wrap.
7. Roll out the dough into a large oval or circle big enough to drop over an 8 or 9-inch pie pan. About ¼ to ⅛ inch thick.
8. Carefully drap the dough over the pie pan, and gently press it down to fit. Trim the excess dough, and crimp the edges between two fingers or with a fork. 
9. Par-bake the crust: Line the pie crust with parchment paper. Place 2 pieces of parchment paper over the pie crust then fill with pie weights. In a small bowl, whisk together 1 egg or egg yolk with 1 Tablespoon water or milk and set aside. Place the pie crust in the preheated oven for 10 minutes then remove from the oven. Carefully remove the pie weights and parchment paper. Prick the bottom of the crust with a fork (don’t pierce through). Brush the base and sides of the crust with the egg wash (not the fluted edge). Return the pie crust to the oven for 7-8 minutes or until the bottom is golden brown. 
10. Place the parbaked pie crust in the refrigerator while preparing the filling.

For the Filling: 

1. Preheat the oven to 400F. Place all the filling ingredients in a bowl, and whisk until smooth. 
2. Pour the filling into the par-baked pie shell. 
3. Place the pie in the oven for 10 minutes. Then, reduce the temperature to 350 degrees Fahrenheit, and let it bake for another 50-60 minutes or until a knife can be inserted 1 inch from the crust and comes out clean. Tip – After half way through baking, be sure to cover the edges of the crust with aluminum foil to prevent over browning. 
4. Let the pie cool or chill in the fridge for at least 2 hours before serving. Garnish as desired. Store the leftover pie, covered, in the refrigerator for up to 4 days.