Prep the pan & room‑temp cream cheese
Line an 8×8‑inch baking pan with two sheets of parchment, laid perpendicular so the paper hangs over all four sides (this creates a sling to lift out the bars later). Let the cream cheese sit at room temperature until softened (about 45 minutes).

2. Make the chocolate pudding layer
In a large bowl, whisk together the instant chocolate pudding mix and 1½ cups of the cold milk until dissolved and slightly thickened (about 2 minutes). Let this rest while you prepare the crust so it continues to set.

3. Prepare the crust

• Melt the 6 tablespoons unsalted butter in the microwave (about 40–60 seconds on HIGH).

• Place the Oreo cookies in a food processor and pulse into fine crumbs (about 12–15 one‑second pulses).

• Drizzle the melted butter over the crumbs, add ¼ teaspoon of kosher salt, and pulse about 5 more times until the mixture holds together when squeezed (or, combine by hand in a bowl).

• Press the crumb mixture into the bottom of the parchment‑lined pan, packing evenly into corners and edges. Refrigerate it while you assemble the fillings.

4. Whip the cream
Using a stand mixer or hand mixer with whisk attachment, beat the cold heavy cream and ¼ cup powdered sugar on high speed until stiff peaks form (2–4 minutes). Transfer this whipped cream into a separate bowl.

5. Make the peanut butter‑cream filling
Without wiping out the bowl, combine the softened cream cheese, ½ cup powdered sugar, ½ cup creamy peanut butter, and the remaining ¼ teaspoon kosher salt. Beat on medium speed until light and fluffy (around 3 minutes), scraping the bowl once. Then take 1 cup of the whipped cream and gently fold it into this peanut butter mixture using a flexible spatula, just until combined.

6. Layer the bars

• Dollop and spread the thickened chocolate pudding over the cookie crust in an even layer.

• Next, dollop and spread the peanut butter cream mixture atop the pudding layer.

• Finally, dollop the remaining whipped cream over the peanut butter layer and spread evenly.

7. Chill
Cover the assembly and refrigerate for at least 4 hours, or preferably overnight, to allow firm setting.

8. Add drizzle and chocolate shavings
Before serving, mix together the remaining 2 tablespoons powdered sugar, 1 tablespoon peanut butter, and 1 tablespoon milk in a small bowl until smooth. Transfer to a zip‑top bag, snip off a corner, and drizzle over the bars. Optionally, use a vegetable peeler to shave pieces from the chocolate bar and scatter on top. Lift the bars out using the parchment “sling” and place on a cutting board. Use a clean, sharp knife (wipe between cuts) to slice into 12 bars.