Cook sweet potatoes. Strain well. Add them back to the pot on medium heat to cook out the rest of the water. Stir them the whole time, this should take less than a minute. Set aside.

Pre heat the oven to 350.

Grease an 8x11 casserole dish with butter and set it aside.

Mash the sweet potatoes in the pot and add 4 cups of mashed sweet potatoes to a large bowl.

While using a whisk, Mix in the sugar.

Mix in the eggs very well, making sure no streaks of eggs are left.

Stir in the butter until smooth.

Mix in the cinnamon and salt.

Stir in the milk and then the vanilla.

Pour it into the casserole dish and smooth out the top. Bake for 35 minutes.

Remove from the oven and turn oven to 500.

Once it reaches temperature add the marshmallows on top of the casserole, then bake for 3-4 minutes or until marshmallows are golden brown. Make sure to keep an eye on it so they do not burn, it may need to come out sooner.

Remove from the oven and cool slightly then serve.