Our grown-up twist on the beloved childhood treat teams a chocolate wafer crust with a decadent peanut butter filling and swirled chocolate ganache topping.
Crust: Preheat oven to 350 degrees. Pulse wafers in a food processor until fine crumbs form. Add butter, granulated sugar, and salt; process until well combined. Press mixture firmly into bottom and up sides of a 10-inch fluted tart pan with removable bottom. Bake until crust is fragrant, about 15 minutes. Transfer to a wire rack and let cool completely.
Filling: Sift confectioners' sugar into a large bowl; set aside. Combine butter, cream, peanut butter, vanilla, and salt in a saucepan over medium heat. Cook, stirring, until butter and peanut butter are just melted. Pour over confectioners' sugar in bowl and whisk until smooth. Pour into cooled crust and spread to edges with a small offset spatula. Cover with plastic wrap, pressing it directly onto surface, and let cool to room temperature, about 30 minutes.
Topping: Place chocolate and butter in a heatproof bowl. Bring cream just to a boil in a small saucepan over medium heat; pour over chocolate mixture. Let stand 5 minutes until chocolate has softened, then stir together with a rubber spatula until emulsified. Let cool at room temperature, stirring occasionally, until ganache is thick, glossy, and just holds a line but is still pourable, 30 to 40 minutes.
Place tart on a revolving cake stand. Pour ganache into center of tart and carefully spread just shy of the edges. Using a small offset spatula held at an angle, create a spiral pattern in the top of the tart by spinning cake stand while slowly sliding spatula out from the center of the tart to the edge. Let stand at room temperature until ganache has set, about 1 hour. Serve at room temperature with whipped cream and peanut brittle, if desired. Tart is best served the same day but can be stored in an airtight container at room temperature up to 2 days.