Preheat your oven to 400 F and line a baking sheet with parchment paper.
Scrub and clean your sweet potatoes.
Leaving the skin ON your sweet potatoes, carefully slice them into 1-inch rounds. Try to make sure that they're approximately the same thickness, so that they cook evenly.
Place your rounds onto a greased baking sheet, and brush them lightly with maple syrup and a sprinkle of cinnamon.
Cover with foil, and bake for about 12 minutes.
While the sweet potato rounds are baking, add the pecans, maple syrup, and cinnamon to a small bowl, mix well, and set aside.
Remove the potatoes from the oven and gently peel back the foil. Gently flip each potato to the other side.
Scoop some of the pecan-maple-cinnamon mixture onto each potato slice (about 1 tablespoon). Cover again with the foil, and put them back in the oven for another 12 minutes.
Remove the potatoes from the oven, and again, gently peel back the foil. Sick a fork into one of the slices to make sure that it's fully cooked through (you should be able to stick a fork in easily. If that’s not the case, cover them again and cook for another few minutes).
Once the sweet potatoes are fully cooked, add about 3-4 mini marshmallows to the top of each one. Then, turn the broiler on and broil for about 30 seconds, until the marshmallows brown. Note: THIS WILL HAPPEN VERY QUICKLY! Keep a close eye on them to make sure they don't burn.
When they're finished, remove from the oven and let cool. Serve on a platter, and enjoy!