Preheat oven to 350 degrees F. Lightly spray 12 (6-ounce) ramekins with cooking spray. Divide the ramekins among 2 baking sheets and set aside.
Cook sweet potatoes in the microwave according to package directions. Empty into a large mixing bowl, add butter and beat with a hand mixer until smooth. Mix the remaining ingredients (except marshmallow topping) and beat until well incorporated. Pour into prepared ramekins and bake in preheated oven for 30 minutes. Remove from the oven and top each souffle with a dollop of marshmallow topping. Brown the topping with a torch or place under the broiler until lightly browned.