Slice 1 extra large sweet potato as thin as you can. Unless you have expert knife skills, a mandolin is your friend.
Melt 1/4 cup coconut oil until its a liquid and toss it with the sliced sweet potatoes and half the 1/2 teaspoon salt and half of the 2 tablespoons fresh minced rosemary in a large bowl.
Using a large muffin tin, add stacks of potatoes.
In a separate bowl, melt 2 tablespoons butter and combine with remaining 1/2 teaspoon salt, 2 tablespoons fresh minced rosemary, and 1/4 cup parmesan. Spoon on top of potato stacks.
Bake in preheated 400℉ oven for 30 minutes or until tender.