Preheat oven to 400 degrees.
Place potatoes on a baking sheet lined with parchment paper or foil.
Bake until fork tender, about 45-60 minutes.
Slice hot potatoes in half lengthwise and scoop out flesh into bowl of a food processor leaving a ¼ inch rim.
To the food processor, add cream, butter, pumpkin pie spice, salt and pepper.
Process until potatoes are smooth.
Spray a baking sheet with non-stick spray.
Place sweet potatoes on baking sheet and add a few marshmallows to each shell.
Spoon mixture back into each shell, sprinkle brown sugar and pecans on top.
Bake at 400 degrees until potatoes are hot, about 10-12 minutes.