Wash and dry the sweet potato then poke some holes in it with a fork, now into the oven at 350 degrees F for 60 to 70 minutes. Or you can boil it for about 50 to 60 minutes. In both cases, it will be done when a fork goes into it easily.
Now once the sweet potato is done, let it cool a bit then peel it. The peel will come right off using your fingers. Then using a fork, mash that sweet potato up. You can optionally use a food processor for this step and all the mixing steps.
Add the softened butter and mix it well with a hand mixer or food processor. Then make sure to scrape the sides and mix again, until the butter is all incorporated nicely. You can use a sturdy whisk as well or a wooden spoon.
Next, add the rest of the ingredients except for the flour (white sugar, brown sugar, milk, cinnamon, nutmeg, vanilla extract, and eggs) and mix it all together until it is nice and combined. Again you may use your food processor if you like.
If the mixture is too runny add flour a tablespoon at a time to thicken it up until the mixture is almost like an applesauce consistency. Do not overdo the flour though, so I wouldn't add anymore than 3 Tablespoons.
Next, place the pie crust in the oven and pre-bake it at 350 degrees F for about 10 minutes, not a necessary step, but it helps to keep the pie crust from getting soggy.
Add the pie mixture to the crust. Scraping the sides as needed to get it all out of the large bowl. Now place it in the oven and bake for 50 to 60 minutes, until the crust is golden brown and the top is not jiggly anymore. Check it after 40 minutes, if the crust is getting too brown, cover it with foil.
The pie will probably puff up a little bit, and that is ok, after you take the pie out of the oven, let it cool for an hour at room temperature, the top will settle back down and be flatter. After an hour, place the pie in the fridge for about 3 hours to set completely. Serve with whipped cream and or pecans if you like! Enjoy!