Preheat the oven to 350 degrees F. Make the crust: Pulse the graham crackers and granulated sugar in a food processor until finely ground. Add the melted butter and pulse a few times until combined. Press the mixture into the bottom and up the side of a 9-inch pie plate, making a thicker rim around the edge. Bake until the top edge is firm and the bottom is dry, about 15 minutes. Transfer to a rack and let cool completely.
Make the filling: Melt the butter and chocolate in a medium saucepan over medium heat, stirring occasionally, until smooth. Transfer to a medium bowl and let cool 5 minutes. Whisk in the granulated sugar, eggs, vanilla and salt until smooth. Whisk in the flour until combined.
Pour the filling into the cooled crust. Bake until the filling is set and a toothpick inserted into the center comes out clean, 30 to 35 minutes. Transfer to a rack and let cool completely.
Make the topping: Combine the heavy cream, marshmallow cream and confectioners' sugar in a food processor and pulse, scraping down the processor, until the mixture is thick. Spoon the topping onto the center of the pie. Top with shaved chocolate.