Boil sweet potatoes: Place cubed sweet potatoes in a large pot, cover with cold water, and bring to a boil. Reduce heat and simmer 15-20 minutes, or until easily pierced with a fork. Drain well.

Mash sweet potatoes: While hot, transfer to a large bowl and mash until smooth using a potato masher, fork, or electric mixer.

Combine wet ingredients: Add melted butter, granulated sugar, brown sugar, eggs, vanilla, cinnamon, nutmeg, cloves, and milk to mashed sweet potatoes. Mix thoroughly.

Pour into baking dish: Pour mixture into a greased 9x13 inch baking dish.

Bake: Bake in a preheated oven at 350°F (175°C) for 30-35 minutes, or until set and lightly browned.

Add marshmallows: Remove from oven and immediately top with marshmallows.

Broil (optional): For toasted marshmallows, broil 1-2 minutes, watching carefully to prevent burning.

Cool and serve: Let cool slightly before serving.