01 -  Preheat oven to 400°F. Prick sweet potatoes with a fork, place on a baking sheet, and roast for 45 to 50 minutes until completely tender. Allow to cool, then peel and mash until completely smooth. Reduce oven temperature to 350°F. 
 02 -  In a large mixing bowl, blend mashed sweet potatoes, brown sugar, melted butter, milk, eggs, white miso, vanilla extract, cinnamon, ginger, nutmeg, and salt. Whisk thoroughly until the mixture is smooth and uniform. 
 03 -  Pour the sweet potato mixture into the prepared 9-inch pie crust and smooth the surface evenly. 
 04 -  Bake at 350°F for 40 to 45 minutes, or until the center is just set and a knife inserted comes out mostly clean. 
 05 -  Transfer the baked pie to a wire rack and let cool to room temperature. Refrigerate at least 2 hours before slicing. 
 06 -  Whip cream with powdered sugar and vanilla extract until soft peaks form. Serve each slice with a dollop of whipped cream and garnish with toasted pecans if desired.