Preheat oven to 375 note if your oven preheats fast then you won't need to start this early but are takes a bit to heat up.

Put a pan on the stove with enough water to cover the potatoes and start heating to boil

Skin sweet potatoes and cut-ups so they are about the same size so they cook evenly about one inch or smaller

Added to the pot of water it is okay if they are just poking out a little bit they will steam cover for about. About 15 minutes or till tender it will depending on the size you cut them it may take longer

Once they are fork tender (where you can poke them and the fork easily goes in)

Strain the water out and then mash them like you would masked potatoes. Before you have them mashed all the way add the heavy cream and the brown sugar to mix it together as your mashing

Once it is all combined and has consistently put in a 9x13 casserole dish and smooth out

I like to add just a little brown sugar to the top for fun in addition to the other brown sugar but that is optional

Then the marshmallow to the top so that there is one layer

Then add to the oven at 375 for about 20 minutes or till marshmallows are golden brown