Instructions

1. Lightly coat an 8x8-inch square baking pan (at least 2 inches high) with cooking spray. Line the pan with 2 sheets of parchment paper, positioning them perpendicular to each other, so that the parchment hangs about 2 inches over all 4 sides of the pan to form a sling.
2. Process 22 Oreo cookies in a food processor until fine crumbs form, 30 to 60 seconds. Drizzle in 5 tablespoons melted unsalted butter and pulse until evenly moistened, about 5 (1-second) pulses. (Alternatively, place the cookies in a re-sealable plastic bag and crush with a rolling pin into fine crumbs. Transfer to a medium bowl and stir in the butter.)
3. Transfer to the baking pan and use the bottom of a flat measuring cup or your hands to firmly press it into an even layer. Freeze for 10 minutes. Meanwhile, make the filling.
4. Beat 1 3/4 cups cold heavy cream in a stand mixer with the whisk attachment on medium speed until firm peaks form, 5 to 8 minutes. Transfer to another bowl.
5. Beat 8 ounces room-temperature cream cheese and 1 cup creamy peanut butter together in the stand mixer (no need to clean) with the paddle attachment on low speed until smooth, 10 to 20 seconds. Gradually beat in the 1 1/2 cups powdered sugar until combined, scraping down the sides of the bowl as needed. Beat in 2 teaspoons vanilla extract.
6. Working in two increments, fold the whipped cream into the peanut butter mixture with a flexible spatula just until combined and no streaks remain.
7. Transfer to the crust and spread into an even layer. Garnish with 4 coarsely chopped Reese’s Peanut Butter Cups if desired.
8. Cover and freeze until set, at least 4 hours or up to overnight. Grasping the excess parchment, lift the slab out of the pan and place on a cutting board. Let sit at room temperature for 15 minutes. Cut into 12 or 16 pieces, wiping the knife clean between each cut for the cleanest-looking slices.