Wash and peel sweet potatoes. Remove all skin and use a paring knife to remove any eyes or bruised flesh. Cube into 1 ½ inch pieces and place in a pot. Make sure the pot is big enough to hold the potato with some extra room. Add cool water to the pot and cover the potatoes completely.
Put the pot on the stove and bring to a boil. Boil sweet potatoes for about 20 minutes or until they are fork tender. Fork tender means you can push a fork easily through the center of the potato chunks and break them apart easily.
Drain potatoes into a colander and return to the pot. Add ¼ cup of butter to the pot and let the hot sweet potatoes soften it. Save the remaining butter for the pecan topping.
In a small bowl beat 1 egg. Add ¼ cup of heavy cream and 1 teaspoon vanilla to the egg and mix together. Add the mixture to the pot. Add salt, pepper, nutmeg, and cayenne pepper to the pot to season.
Using a hand mixer or potato masher mash the cooked sweet potatoes. Make sure to smash away all the lumps and stir all the ingredients in evenly. If you are using a hand mixer, be careful not to over mix.
Transfer the mashed sweet potatoes to an oven safe casserole dish. Preheat oven to 375°
In a microwave safe bowl, melt the remaining ½ Cup of butter. Add ½ cup of brown sugar, 1 teaspoon cinnamon, and 1 Cup chopped pecans to the butter and mix together with a fork. Spread the Butter Pecan Topping over the top of the mashed sweet potatoes evenly.
Place in a preheated 375° oven for approximately 20 minutes. Serve and enjoy.