Wash and cut up the sweet potatoes. In a large pot of boiling, salted water, cook until soft enough to mash—about 12-15 minutes.
Drain well and then mash in a large bowl.
To the bowl add the egg, 1/4 cup brown sugar, milk, 1/4 cup butter (softened), salt, cayenne, pepper and 1/4 teaspoon cinnamon. Mash together.
In a greased 9×13 pan, spread the sweet potato mixture in an even layer.
To make the brown sugar pecan topping, in a medium size bowl, stir together the 1/2 cup brown sugar, all-purpose flour, 1/4 cup butter (softened) and chopped pecans. This mixture should be crumbly. Spread evenly over the casserole before baking.
If you are using mini marshmallows for the topping, wait to add them until the last 5-8 minutes of baking.
Bake the casserole at 350°F (177°C) for 25-30 minutes.
Notes
The get the marshmallow topping that extra crispy, caramelized top, you can pop the finished casserole under the broiler for a minute or two (keep a close eye!) or use a kitchen torch to brulee the tops of the marshmallows.If your family is divided on toppings and you want to do a half and half casserole similar to the one I have pictured, keep in mind the measurements for the toppings in the recipe card are to cover the entire casserole. So, you want to divide them in half.You can easily make sweet potato casserole ahead of time; simply keep the topping items separate and cover the refrigerate the casserole until you’re ready to bake.The nutrition facts on this recipe card include both toppings, as both ingredients are listed.