Preheat your oven to 400°F (200°C). Drain the canned yams and place them in an 8x8-inch casserole dish, spreading them out evenly.

Mash the yams directly in the casserole dish with a potato masher or fork until they reach your desired consistency. I like to leave mine a little chunky for some texture.

Pour the melted and slightly cooled butter over the mashed yams. Add the dark brown sugar and stir until well combined, ensuring the mixture is evenly sweetened.

Sprinkle ground cinnamon evenly over the yam mixture. Add the mini marshmallows on top, covering the surface. To prevent the marshmallows from sticking, spray the underside of a piece of foil with nonstick spray and cover the dish.

Bake the casserole covered for 20 minutes. Then remove the foil and bake for an additional 5-10 minutes, or until the marshmallows are golden brown and gooey. Let cool slightly before serving for the best texture.