Wash the sweet potatoes and poke the skins several times with a fork. Season with salt and black pepper and wrap the potatoes in tin foil, twisting the ends.
Bake on a baking sheet for 45-50 minutes, until potatoes are tender. Let them cool for 15-20 minutes then cut them in half and scoop out the potato from the skins. Be sure to leave a nice buffer for yourself between your scooping and the skin of the potato.
Add the scooped potato into a large bowl. Use your hand masher to mash your sweet potato slightly. Add butter, milk, brown sugar, vanilla, and cinnamon. Stir well to combine.
Fill the sweet potato skins with the sweet potato mixture. Place back in the oven to reheat and remove and top with miniature marshmallows.
Toast the marshmallows by using a culinary torch or by placing the potatoes back into the oven with the broil setting on low. Watch carefully, they toast up quickly, in about 1-2 minutes.