Food processor method: Add the flour and salt to the food processor, along with the vegan butter. Pulse to break the clumps. Add the ice cold water, and continue to pulse until the pieces of dough are about the size of a split pea. Transfer the dough to a floured surface and form into a tight ball. Do not knead it; just shape into a ball. Wrap the dough in plastic and refrigerate it for at least 2 hours or overnight.
By Hand Method: In a large bowl, combine flour and salt. Add the vegan butter and use a pastry cutter to blend it until the mixture resembles coarse crumbs. Add the ice cold water and stir with a wood spoon to combine.Wrap your dough in plastic and refrigerate it for at least 2 hours or overnight.
When ready to bake preheat oven to 350°.
Generously flour your work surface, and use a rolling pin to roll the dough out flat (about 1/6 inch). Gently place it over your pie dish, and press evenly to the bottom and sides.
Combine sweet potato puree and arrowroot powder in a large mixing bowl, and set aside.
In a sauce pan combine the vegan butter, soy milk, sugar, chocolate chips, maple syrup, vanilla, and sea salt. Use a whisk to break up any clumps in the mixture as it simmers.
Cook for about 3 minutes, then remove from heat.
Slowly pour the sugar mixture into the bowl with the sweet potato and arrowroot, and stir well. There should be no clumps.
Pour the filling into the prepared pie crust and bake for 45-50 minutes.
Remove from oven and allow to cool for at least an hour.