How to Make It
Heat the oven to 425°.
Roll the dough out to a round 1/4 inch thick and line a 9-inch pie pan with it, trimming the edges. Prick all over with the tines of a fork, line with parchment paper, and fill with pie weights or dried beans. Bake for 20 minutes, then remove the paper and weights and continue to cook until golden brown, about 12 minutes more. Let cool completely.
In a bowl, stir together the confectioners’ sugar and 1/2 cup of the peanut butter with a fork until it forms crumbles (you’ll see what I mean when it gets there); reserve 1/2 cup of the crumbles and refrigerate until ready to use. Spread the remaining crumbles in the bottom of the cooled crust.
In a medium-size saucepan, whisk together the brown sugar, cornstarch, and salt, then add the egg yolks, stirring until smooth. Whisk in the milk until smooth, then bring to a simmer over medium heat. Cook the custard, whisking constantly, until it thickens to the consistency of loose pudding, then continue to cook for another minute. Remove from the heat and whisk in the remaining 1/2 cup peanut butter until smooth. Add the butter and 1 tablespoon of the vanilla and whisk until smooth and emulsified. Pour the custard over the crumbles in the pie shell and smooth the top with a rubber spatula. Refrigerate until well chilled and set, at least 4 hours or up to overnight.
When ready to serve, whisk together the remaining 1 teaspoon vanilla, the cream, and granulated sugar until stiff peaks form, then spread evenly over the pie, creating peaks and valleys in the cream with your spatula. Sprinkle the reserved crumbles on top of the whipped cream, letting them fall into the valleys. Serve chilled.