Preheat oven to 400 degrees Fahrenheit.
Drain yams and add to an 8 b y 8 casserole dish.
Mash to your desired consistency with a potato masher or fork.
Add melted butter and brown sugar to the yams and stir to mix.
Sprinkle mixture with cinnamon and top with mini marshmallows.
Spray the underside of a piece of foil with nonstick spray to prevent sticking to the marshmallows and wrap the baking dish.
Bake for 20 minutes covered. Remove foil and bake another 5-10 minutes or until marshmallows are golden brown.
