I had originally intended on making twice baked sweet potatoes but couldn't get the potatoes to keep their shape. So I came up with this casserole, which turned out great! It's so sweet you might even want to serve it as a dessert! :o)
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. Let rest until cool enough to handle.
Handling the potatoes with a pot holder, slice each in half lengthwise and scoop out the flesh into the bowl of a food processor. To the food processor add the heavy cream, butter, pumpkin pie spice and salt and pepper. Process until potatoes are silky smooth.
Place sweet potato mixture into a 2-quart casserole dish. Sprinkle brown sugar and pecans on top. Bake at 400 degrees for about 15 minutes. Add marshmallows to top and broil for 5 minutes until marshmallows are browned. Serve warm.