Place unpeeled sweet potatoes in a large pot of water and bring them to a boil. Cook until fork-tender, about 40 to 50 minutes
Preheat the oven to 350 degrees Fahrenheit (175°C).
Take sweet potatoes out of the pot and run them under cold water. Peel off the skin and roughly chop the sweet potatoes.
Place the chopped potatoes in a strainer and allow them to dry.
Put the dry potatoes into a large bowl and gently mash. Then, add the butter and beat with an electric mixer until well combined and lump-free.
Add the sugar, milk, eggs, nutmeg, cinnamon, and vanilla. Beat at medium speed until the mixture is smooth.
Pour and spread the filling evenly into the pie crust.
Bake for 55 to 60 minutes or until a knife inserted into the center comes out clean. Let the pie cool before serving. Enjoy!