Slice the potato as thin as you can. Unless you have expert knife skills, a mandolin is your friend.
Melt coconut oil until its a liquid and toss it with sliced sweet potatoes and half the salt and rosemary in a large bowl.
Using a large muffin tin, add stacks of potatoes.
In a separate bowl, melt butter and combine with remaining salt, rosemary, and parmesan cheese. Spoon on top of potato stacks.
Bake in preheated 400 degree F oven for 30 minutes or until tender.