Line a 7-inch springform or pie pan with removable bottom with parchment paper and grease it with a little oil. Set aside.
Cook or boil one sweet potato until it's soft and let it cool completely, then mash it with a potato masher.
Process all crust ingredients in a food processor. Start with the nuts (or seeds) and oats and then add the dates and vanilla extract. Process until the mixture sticks together when you press it between your fingers. If it's too dry, add more dates.
Press the crust evenly into the bottom of the pie pan and up the sides. Set aside.
Melt the chocolate chips in a double-boiler or in the microwave and process all cream ingredients in a food processor or blender until completely smooth and creamy.
Spoon the cream on the crust and spread it evenly. Put the pan in the fridge overnight to set. You could also freeze it until it firms up (check after about an hour).
For the optional chocolate drizzle, simply melt chocolate chips in a double-boiler or in the microwave and pour it over the pie. Spread immediately.
Refrigerate or freeze for some minutes, then cut into pieces and enjoy!