Bring the chunks of sweet potatoes to a boil in a medium saucepan that’s filled with water just covering the sweet potatoes. Reduce the heat to low, then cover and simmer about 15-20 minutes or until sweet potatoes are very tender.
While the sweet potatoes simmer, roll out your prepared, chilled pie crust to about 12-14 inches in diameter.
Carefully place the rolled-out dough into a 9-inch pie plate. Fold the excess pie dough under, then crimp the edges with a fork. Place the prepared pie crust into either the refrigerator or freezer as you work on the sweet potato filling.
Adjust oven rack to 2nd level position (just above center), place a jelly roll pan or baking sheet on the rack, and preheat oven to 425ºF.
Drain the sweet potatoes in a colander, then transfer to a mixing bowl of a stand mixer fitted with a paddle attachment.
Beat the sweet potatoes on medium-high speed until completely mashed and smooth.
Add in the remaining 11 ingredients (the unsalted butter to the salt) and beat on medium-high speed until well blended and smooth.
Pour the sweet potato pie filling into the chilled pie crust, then with a pastry brush, lightly brush the crimped edges of crust with egg wash. You won't use the entire amount of egg wash.
Place the pie on directly top of the heated jelly roll pan or baking sheet in the oven. Bake for 425ºF for 15 minutes.
Keeping the oven door closed, reduce the oven temperature to 350ºF and continue to bake for another 40-45 minutes. At this time, you can choose to add a silicone pie crust shield or a sheet of aluminum foil with a hole cut out to avoid over baking the crust.
Your sweet potato pie will be ready to remove from the oven when there is still some jiggle in the center.
Remove from oven and allow pie to cool and set on a wire cooling rack for at least 2-3 hours. As the pie cools, it will settle. Once cooled, place in the refrigerator to chill.
Decorate with marshmallow meringue, whipped topping, or pipe a cream cheese frosting design onto the top. These are all optional toppings. This brown sugar sweet potato pie is perfect as-is too!