In a small bowl cut the butter into the sugar, flour, oats and cinnamon with a fork or pastry blender until small pea shaped crumbs form. Set aside.
Preheat oven to 400°F. Prick each sweet potato a few times with a fork and place on a lined baking sheet.Bake for 45-50 minutes, or until tender.
When cool enough to handle slice lengthwise and carefully scoop out the tender potato, leaving a 1/4 inch thick border. Discard 2 of the skins and keep remaining 8 empty skins on baking sheet.
Mix the sweet potatoes, butter, brown sugar, pumpkin spice and salt by hand or electric mixer. Taste and season again to adjust with salt if needed.
Add half of the bacon, half the Oat Crumb Topping and all the marshmallows, stirring to combine. Carefully scoop filling back into 8 of the 10 skins (See Note 1). Top with remaining Oat Crumb Topping and bacon, distributing evenly. (See Note 2).
Place the sweet potatoes in a 400°F oven and bake for 20 minutes. Serve immediately.
I like these filled so by having more filling than skins is best. Save remaining two skins for other use if you like.
At this point the sweet potatoes can be covered with plastic wrap and refrigerated for up to 2 days and then baked or frozen for later use.