01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan thoroughly.
02 - Prepare chocolate cake mix according to package directions. Pour batter into prepared pan and bake for 30-35 minutes until a toothpick inserted in the center comes out clean.
03 - Let cake cool for 10 minutes. Using the handle of a wooden spoon, poke holes all over the surface, spacing about 1 inch apart.
04 - In a medium bowl, whisk together pudding mix and cold milk for 2 minutes until slightly thickened. Stir in peanut butter until smooth and fully incorporated.
05 - Pour peanut butter pudding evenly over the warm cake, spreading gently to ensure all holes are filled. Cover and refrigerate for at least 1 hour.
06 - In a large bowl, beat heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Spread whipped cream evenly over the chilled cake.
07 - Microwave chocolate chips, peanut butter, and heavy cream in a small bowl for 30 seconds. Stir until smooth; microwave an additional 10 seconds if needed. Drizzle over whipped cream layer.
08 - Sprinkle chopped peanuts and arrange halved peanut butter cups on top. Refrigerate for 30 minutes before serving for optimal texture and flavor.