Cup of Yum
1. Preheat oven to 350 degrees F.
2. Butter or spray with baking spray a 9x13-inch casserole or baking dish. Set aside.
3. Add 2 cups of pecans to a baking sheet and roast for a few minutes, watching closely to prevent burning. Remove from oven, cool, and roughly chop.

Cook the Potatoes:

Cup of Yum
1. Peel, cube, and wash sweet potatoes. Add the cubed potatoes to a Dutch oven or large saucepan. Cover with water and bring to a boil. Boil for about 15 minutes. When pierced with a fork, the potatoes should be tender.
2. Drain cooked sweet potatoes, mash, and set aside to cool off a bit.

Cinnamon Filling:

1. While the potatoes are cooking, in a small bowl, use a fork to mix the softened butter, flour, sugar, and cinnamon together until soft crumbs form. Set aside.

Pecan Topping:

1. Combine all the ingredients from the "Pecan Topping" section except marshmallows. Stir and set aside.

Sweet Potato Layer:

1. Combine the slightly cooled mashed potatoes with the ingredients from the "For the Potatoes" section: brown sugar, melted butter, 1 cup chopped pecans, lightly beaten eggs, milk, salt, vanilla, cinnamon, and nutmeg. Stir to combine until smooth.

Assembling the Casserole:

1. Add half of the mashed sweet potato mix to the prepared pan, distribute evenly, and smooth the top with a spatula.
2. Sprinkle half of the Cinnamon Filling mixture on top of the mashed potatoes.
3. Add the remaining sweet mashed potato filling, distribute evenly, and smooth the top with a spatula.
4. Sprinkle the Pecan Filling mixture on top of the mashed potatoes.
5. Sprinkle the mini marshmallows if using them.
6. Sprinkle the remaining Cinnamon Filling mixture on top.

Bake:

1. Bake for 30 minutes, until the filling is hot and the topping has browned.
2. If the marshmallow starts to brown too quickly, spray some foil with baking spray and cover the casserole, greased side down, being careful not to touch the toppings.
3. Serve warm.