Preheat the oven to 325 degrees F.
Line an 18x26-inch baking sheet with parchment paper.
In a large bowl, add the flour, the cocoa powder, the granulated sugar, 1 1/2 teaspoons of the cornstarch, and 1 1/2 teaspoons of the salt and whisk to combine.
In a microwave-safe bowl, add 1/2 cup plus 1 tablespoon of the butter and melt in the microwave on high power.
Add the melted butter to the flour mixture and stir until it forms into rough clumps.
Knead the crust mixture until no loose dry ingredients remain.
Spread the crust mixture onto the prepared baking sheet and bake, stirring after 10 minutes, until it is fragrant and dried out, about 20 minutes.
Transfer the baking sheet to a wire rack and let the crust cool completely.
In a food processor, add the cooled crust and pulse until it is finely ground.
In a second microwave-safe bowl, add the remaining butter and melt in the microwave on high power.
Add the remaining melted butter to the crumb mixture and pulse until the crumbs are evenly moistened.
Pour the crumb mixture into an ungreased 9-inch pie plate and evenly press it into the bottom and up the sides.
Bake the crust until it is set, about 12 minutes.
Transfer the pie plate to a wire rack and let the crust cool while making the filling.
In medium saucepan with the stovetop heat off, add the brown sugar, the remaining cornstarch, and the remaining salt and whisk to combine.
Add the egg yolks to the brown sugar mixture and whisk until a smooth, thick paste forms.
Turn the stovetop on medium heat. Add the milk to the filling mixture and cook, stirring constantly, until it bubbles and thickens into a pudding, about 8-10 minutes.
Transfer the saucepan to a wire rack. Add the peanut butter and the vanilla extract to the filling and whisk until it is smooth.
Immediately pour the filling into the cooled crust and smooth out the top.
In a third, large, microwave-safe bowl, add the chopped chocolate.
In a small saucepan over medium heat, bring the heavy cream to a simmer.
Immediately pour the hot cream over the chopped chocolate and let it stand, about 1 minute.
Using a spoon and starting in the center of the mixture, slowly stir the chocolate mixture until it emulsifies into a shiny sauce.
Pour the ganache mixture over pie, then pick it up and carefully tilt it so the ganache evenly coats the filling layer.
Sprinkle the ganache layer with the peanuts.
Place the pie in the refrigerator and let it chill until the filling and the ganache are set, for at least 2 hours and up to overnight.
Sprinkle the pie with the sea salt.
Slice and serve.