Prepare pie crust. In the bowl of a stand mixer fitted with the paddle attachment, sift together the almond flour, baking cocoa, oat flour, tapioca flour, sugar, and salt. (Alternatively use a food processor or hand mixer).
Add butter cubes and drizzle with vanilla and chocolate extracts. Beat on medium-low until dough begins to clump when pinched with your fingers and the butter is completely combined, about 3-5 minutes. If using the food processor, pulse until the dough begins to clump together.
Dump the dough into a 9-inch springform pan, a 10-inch deep-dish pie pan, or a 9-inch pie pan (If using a 9-inch pie pan, you may use a little less dough). Press the dough evenly into the pan, starting up the sides 1½-inches and then moving to the bottom. Your crust should be between ⅛ and ¼-inch thick with the top edges squared off. Prick the bottom all over with a fork, place on a baking sheet, and chill in the fridge or freezer until firm, 15-30 minutes for the fridge, 10 minutes in the freezer.
Meanwhile, preheat the oven to 375°F.
When the crust is firm, bake on the middle rack for 16-18 minutes, or until it looks firm, but does not yet smell burnt or look too dark. Remove from oven and while the crust is still hot, use the back of a spoon to gently press down on the sides and bottom to help hold it together as it cools. While the crust is still hot, dump the finely chopped chocolate inside the shell. Let it sit for 2-3 minutes, then use a spoon to swirl the chocolate into the bottom and up the sides of of the shell. Chill in the fridge or freezer while you prepare the filling.
In the bowl of a stand mixer with the whisk attachment or a mixing bowl with a hand mixer, whip the mascarpone, 1½ cups powdered sugar, salt, and vanilla until smooth and soft peaks form, about 2-3 minutes.
Remove 2/3 of the filling and set aside in a separate bowl. Prepare the chocolate layer: To the mixing bowl with 1/3 of the filling, add the cocoa powder, 3/4 cup heavy cream, and chocolate extract. Whisk on medium high speed until smooth and soft peaks form, 1-2 minutes.
With the mixer running on low, slowly pour in the melted cooled chocolate and mix until completely smooth and firm (but not too stiff) peaks form, adding another 1-2 tablespoon heavy cream, if needed. Pour into chilled baking crust, scraping out the mixing bowl as much as possible, and use a rubber spatula or off-set spatula to create an even smooth layer. Chill while you prepare the peanut butter layer.
In the same mixing bowl (no need to clean it), add the remaining 2/3 of the filling, peanut butter, remaining ½ cup heavy cream, and remaining 1/4 cup powdered sugar. Whisk on medium-high speed until smooth and firm (but not too stiff) peaks form. Pour over chilled chocolate later and smooth into an even layer, adding decorative swirl if you like.
Garnish with chopped peanut, shaved chocolate, and flaky salt. Chill until firm, at least 4 hours or overnight. This pie keeps for 3-4 days in the refrigerator, so it's perfect to make in advance!
Note: this recipe was prepared for Rodelle by @snixykitchen. Click here to see the original post with more helpful hints!
