Line an 8x8-inch baking pan (about 2 inches high) 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.

Whisk 1 (3.9-ounce) box instant vanilla pudding mix and 1 ½ cups of the cold whole milk together in a large bowl until the pudding is dissolved. Whisk in 1 cup of the creamy peanut butter until combined. Let sit to thicken while you prepare the crust and other layers.

Break 22 of the Nutter Butter cookies into pieces and place in a food processor. Pulse until fine crumbs form, 12 to 15 (1-second) pulses (about 2 ¾ cups).

Drizzle 6 tablespoons melted unsalted butter over the cookie crumbs, and add ¼ teaspoon of the kosher salt. Pulse until it resembles wet sand and holds together when squeezed, about 5 (1-second) pulses.

Transfer the mixture into the pan. Use the bottom of a measuring cup or your fingers to press the crumbs into an even layer, making sure to reach the edges and fill the corners. Refrigerate while you make the filling.

Beat 1 ½ cups cold heavy cream and ¼ cup of the powdered sugar with the whisk attachment in a stand mixer on high speed until stiff peaks form, 2 to 4 minutes.

Transfer 1 cup of the whipped cream to the peanut butter mixture and gently fold together with a flexible spatula until just combined. Transfer the remaining whipped cream to another bowl.

Beat 8 ounces room temperature cream cheese, ½ cup of the powdered sugar, and the remaining ¼ teaspoon kosher salt with the whisk attachment in the now-empty stand mixer (no need to wipe clean) on medium speed, scraping down the sides of the bowl with a flexible spatula halfway through, until light and very fluffy, about 3 minutes total.

Dollop the cream cheese mixture over the crust and spread into an even layer. Dollop the peanut butter mixture over the cream cheese mixture and spread into an even layer. Dollop the remaining whipped cream over the peanut butter layer and spread into an even layer. Cover and refrigerate for at least 4 hours or up to overnight.

When ready to serve, stir the remaining 2 tablespoons powdered sugar, 1 tablespoon peanut butter, and 1 tablespoon whole milk together in a small bowl with a fork until smooth. Transfer to a small zip-top bag, press down into a corner, and snip the corner off of the bag. Drizzle the peanut butter mixture over the delight. Crush the 4 remaining Nutter Butter sandwich cookies into coarse pieces and scatter evenly over the top.

Grasping the excess parchment, lift the slab out of the pan and onto a cutting board. Cut into 12 pieces, wiping the knife between each cut for cleaner cuts.