To make the two cups of sweet potato puree, place a few whole sweet potatoes in large pot, cover with water, and bring to a boil. Boil 40-50 minutes until soft and the skin falls easily off. Remove skin and mash the sweet potato in a bowl with a potato masher until you have a smooth puree.
Preheat oven to 350 degrees F.
In a mixing bowl, add the sweet potato puree, coconut cream, soy milk, light brown sugar, granulated sugar, cornstarch, pumpkin pie spice, vanilla extract, and salt. Using an electric hand mixer (or a whisk), mix until mostly smooth. Tap the bowl on the table to remove any air bubbles.
Pour the sweet potato pie filling into a prepared crust (no need to par-bake, it works great in a raw crust too and saves time!) and smooth the surface. Place the pie on a baking sheet and put it in the preheated oven to bake for 75 minutes. Check at 40-minutes and if the edges are getting dark, tent with foil.
At 75 minutes, turn off the oven and open the oven door partially (a few inches or all the way) to allow the pie to cool for one hour. Once cool, place in the fridge to set for at least 4 hours (or overnight).
Serve with whipped cream, if desired. Store leftover pie in the refrigerator.