Instructions

for the pie crust

Adjust oven rack to lower-middle position and heat oven to 375 degrees. Line rimmed baking sheet with parchment paper. Roll pie dough into 12-inch round on lightly floured counter. Roll dough loosely around rolling pin and unroll onto prepared baking sheet. Using tines of fork, prick holes all over dough. Brush evenly with heavy cream and sprinkle with sugar. Bake until crust is golden brown, 14 to 18 minutes, rotating sheet halfway through baking. Let crust cool to room temperature on sheet on wire rack, at least 30 minutes. Break crust into ½-inch pieces. (Pie crust pieces can be stored in airtight container for up to 1 day.) 

for the candied walnuts

Line second rimmed baking sheet with parchment paper. Heat sugar and butter in 10-inch nonstick skillet over medium heat until bubbling, about 2 minutes. Stir in walnuts until well coated. Continue to cook, stirring often, until mixture darkens slightly and has nutty aroma, 3 to 4 minutes. Stir in vanilla. Immediately pour nut mixture onto prepared sheet and sprinkle with salt. Let cool to room temperature on sheet on wire rack, at least 30 minutes, then chop coarse. (Candied walnuts can be stored in airtight container for up to 5 days.) 

for the sweet potato ice cream

Whisk sweet potato puree, egg yolks, condensed milk, ginger, cinnamon, and nutmeg together in medium bowl. Bring cream, milk, sugar, and salt to simmer in large saucepan over medium heat, stirring often until sugar dissolves. Slowly whisk 1 cup of hot milk mixture into egg mixture to temper, then slowly whisk tempered egg mixture into remaining milk in saucepan. Cook over medium heat, whisking constantly, until mixture is thickened, bubbling, and registers 180 degrees, 6 to 8 minutes (custard should have consistency of thick pudding). Strain mixture through fine-mesh strainer into clean bowl, then stir in vanilla. Let cool until no longer steaming, 10 to 20 minutes. Cover bowl with plastic wrap and refrigerate until well chilled, at least 4 hours and up to 24 hours. 
Transfer chilled custard to ice cream machine. Churn until mixture resembles thick soft-serve ice cream and registers about 21 degrees, 15 to 25 minutes. With machine running, slowly add pie crust pieces and continue to churn until incorporated, 1 to 2 minutes. Transfer ice cream to airtight container, cover with plastic wrap, and freeze until firm, at least 2 hours or up to 2 days. 

for the maple whipped cream

Cut vanilla bean in half lengthwise. Using tip of paring knife, scrape out seeds. Using stand mixer fitted with whisk attachment, whisk cream cheese, maple syrup, vanilla seeds, and salt on medium-low speed until light and fluffy, 1 to 2 minutes, scraping down bowl as needed. Reduce speed to low and add heavy cream in slow steady stream. When almost fully combined, increase speed to medium-high and beat until mixture holds soft peaks when whisk is lifted, 1 to 2 minutes, scraping down sides of bowl as needed.
Scoop ice cream into sundae glasses or bowls. Sprinkle with candied walnuts. Dollop with maple whipped cream and serve.