For a marshmallow version, layer mini marshmallows over the casserole before baking and cook for about 25 minutes until puffed and lightly browned.
If avoiding nuts, replace pecans with ½ cup of rolled oats for added texture.
To prepare in advance, assemble the sweet potato base and place it in a dish. Prepare the topping separately. Store both covered in the refrigerator for 1–2 days, then add topping just before baking.
For freezing, assemble the unbaked casserole, wrap tightly with double layers of foil, and freeze for up to 3 months. Thaw overnight in the refrigerator and allow it to sit at room temperature for 30 minutes prior to baking.