Place the dry ingredients in a food processor. Pulse to mix.  Cut the cold butter into tablespoon size slices and add to food processor.  

Pulse until mixture is crumby.  Add the egg. Pulse until a dough ball forms.

Prepare 2 large sheets of wax paper.  Dust one wax paper sheet with tapioca starch.  Remove the dough ball from the food processor and place in the center of the wax paper.

Add the other wax paper sheet to the top of the dough ball.  Using a rolling pin, roll out dough ball until it forms an even oval shape.  

Carefully remove the top sheet of wax paper and move your oval of pie crust dough to a 10" pie plate.  (I like using glass pie plates.)  Placing the dough side to the pie plate.

Slowly remove the wax paper and begin to shape the pie crust into the pie plate.  Finish the edges however you desire.  Set aside & prepare the seeet potato filling.