Step 1:
Prepare the brownie batter according to the package instructions. Pour it into a greased 12×9-inch baking pan.
Step 2:
Bake at 350°F (175°C) for 20–25 minutes. When a toothpick inserted in the center comes out with moist crumbs, it’s ready.
Step 3:
Let the brownies cool on a wire rack. Once cooled, cut them into slices about ¾-inch thick. Slice the peanut butter cups in half and set aside for garnish.
Step 4:
In a large bowl, whisk the instant vanilla pudding mix with cold milk for 2 minutes until thickened. Stir in the vanilla extract and creamy peanut butter until fully combined. Fold in 1½ cups of the whipped topping.
Step 5:
In a 5-quart glass dish, layer one-third of the brownies, then half of the halved peanut butter cups, and one-third of the pudding mixture.
Step 6:
Repeat the layers two more times. Finish by spreading the remaining whipped topping on top and sprinkling the reserved peanut butter cups as garnish. Refrigerate for a few minutes before serving.