By Jessie Sheehan, JessieSheehanBakes.com
To make the crust
Place the peanut butter in the freezer for at least two hours, or more, until frozen. Combine the flour, granulated sugar, baking powder, salt, and chopped peanuts in the bowl of a food processer fitted with the metal blade and process to combine. Cut the butter and frozen peanut butter into cubes, add to the food processer, and pulse until the mixture includes a combination of coarse crumbs and some larger bits of butter and peanut butter.
Dump the mixture into a large bowl, add the water and vinegar and mix with a wooden spoon until the dough comes together, adding a bit more water, a teaspoon at a time, if necessary. Using your hands, knead the dough in the bowl to incorporate all of the crumbly bits, shape into a large flat disc, wrap in plastic wrap, and refrigerate for at least 2 hours, or preferably overnight. Remove the dough from the refrigerator. Lightly flour a work surface and roll the dough into an 11 or 12-inch circle, and place it into a 9-in [23-cm] pie plate. Decoratively crimp the edges. Freeze for at least 1 hour.
Preheat the oven to 425 degrees F [220 degrees C]. Line the piecrust with parchment paper and fill with pie weights (uncooked brown rice or dried beans work). Combine the egg and salt in a small bowl to make an egg wash and brush it on the crimped edges. Bake the crust for about 20 minutes, until the crimped edges are brown and the bottom of the crust looks dry when you gently lift the parchment paper. Remove the paper and weights and using the tines of a fork, prick the bottom of the crust all over. Return the crust to the oven until the bottom is nicely browned, about 15-20 minutes more. Remove from the oven and brush the bottom with egg wash to seal it (this helps prevent a soggy bottom). Place in the oven for two minutes, until the egg sets. Set aside to cool.
To make the chocolate filling
In a medium heatproof saucepan, add the cocoa powder, granulated sugar, cornstarch, and salt and whisk together. Add the milk and heavy cream and whisk again. Over medium-to medium-high heat, whisk the pudding until it thickens and large bubbles begin popping up on the surface, 5 to 7 minutes. Continue whisking for 1 to 2 minutes more, before removing the saucepan from the heat. Add the vanilla and chocolate and whisk to melt the chocolate. Transfer the pudding to the piecrust, cover the surface with plastic wrap and refrigerate to set up, about 4 - 6 hours, but preferably overnight.
To make the peanut butter whipped cream
Combine all of the ingredients in the bowl of a stand mixer fitted with the whisk attachment, or in a large mixing bowl, and using a hand held mixer, and whisk the cream until medium peaks form. Generously spread the cream over the cool and firm pudding and place in the refrigerator to set up briefly before serving, about 30 minutes. Serve slices sprinkled with chopped salted peanuts.