Preheat your oven to 350°F (175°C) and lightly grease a 9-inch (23 cm) pie pan. In a bowl, mix the graham cracker crumbs, sugar, and melted butter until well combined. Press the mixture evenly into the pie pan to form the crust.
In a microwave-safe bowl, melt the dark chocolate with the butter until smooth.
Spread the melted chocolate over the crust and let it set slightly.
In another bowl, combine the mashed sweet potato and pumpkin with brown sugar, cream, eggs, cinnamon, nutmeg, vanilla, and salt. Mix everything until smooth and creamy.
Pour the sweet potato filling over the chocolate layer and smooth the top with a spatula.
Sprinkle the mini marshmallows evenly over the filling.
Bake for 20–25 minutes, or until the filling is firm and the marshmallows are puffed and golden.
Let the pie cool completely before slicing. For the best texture, chill it in the fridge before serving.