For the brownie: Preheat the oven to 350 degrees F.
Grease a 9-inch deep-dish pie plate with 1 tablespoon butter, then dust with flour. Tap out any excess.
Microwave 4 tablespoons butter in a small microwave-safe bowl in 30-second intervals until melted, about 1 minute. Add the peanut butter cookies to the bowl of a food processor and process until fine crumbs have formed. Pour in the melted butter and pulse until the cookies are wet like sand. Press the cookie crumbs into the bottom and completely up the sides of the prepared pie plate.
Whisk the flour, cocoa powder and salt in a medium bowl. Melt the semisweet chocolate and the remaining 8 tablespoons butter in a medium saucepan over medium heat, stirring constantly to prevent burning, about 2 minutes. Stir in the eggs and sugar until well combined. Gently fold in the flour mixture until well combined. Fold in the peanut butter chips. Pour the batter in the cookie crust and bake until a toothpick inserted in the center comes out clean, 30 to 35 minutes. Remove to a wire rack to cool completely, about 1 hour.
For the peanut butter cream: Meanwhile, place the cream cheese, peanut butter and marshmallow creme in a medium bowl. Beat with an electric mixer on medium speed until smooth. Add the heavy cream to a separate medium bowl and beat with an electric mixer on medium speed until stiff peaks form, about 2 minutes. Fold the whipped cream into the peanut butter mixture, then fold in the mini chocolate chips. Spread the mixture on the top of the pie and chill until completely set, about 2 hours.
For the whipped topping: Meanwhile, whisk the cream cheese, heavy cream and sugar in a medium bowl with an electric mixer on medium speed until stiff peaks form, about 3 minutes. Mound the whipped topping on top of the pie and sprinkle with more mini chocolate chips and peanut butter chocolate chips.
When measuring flour, we spoon it into a dry measuring cup and level off excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)
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