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 toothpick inserted in center comes out clean.
03 - Let cake cool for 10 minutes. Using handle of wooden spoon, poke holes all over cake surface, spacing about 1 inch apart.
04 - Whisk together instant vanilla pudding mix and cold milk for 2 minutes until slightly thickened. Stir in creamy peanut butter until smooth and fully incorporated.
05 - Pour peanut butter pudding mixture evenly over warm cake, using spatula to spread filling into all holes. Cover and refrigerate for at least 1 hour.
06 - Beat heavy whipping cream, powdered sugar, and vanilla extract in large bowl until stiff peaks form. Spread whipped cream evenly over chilled cake.
07 - Microwave semi-sweet chocolate chips, creamy peanut butter, and heavy cream in small microwave-safe bowl for 30 seconds. Stir until completely smooth; microwave additional 10 seconds if needed. Drizzle over whipped cream layer.
08 - Sprinkle chopped roasted peanuts and arrange halved mini peanut butter cups on top. Refrigerate for 30 minutes before serving for optimal texture and flavor.