Preheat your oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish and set aside.

In a medium bowl, whisk together the chocolate pudding mix and milk until smooth. Set aside to thicken for a few minutes.

Pour the chocolate pudding evenly into the prepared baking dish.

Sprinkle the dry chocolate cake mix evenly over the pudding layer.

Drizzle the melted butter and peanut butter over the cake mix. Use a spoon or knife to gently swirl it into the top layer without fully mixing.

Scatter the chopped mini peanut butter cups and chocolate chips over the top, pressing them lightly into the batter. Add chopped peanuts if desired.

Bake in the preheated oven for 35-40 minutes, or until the edges are set and the center is slightly gooey.

Let the cake cool for about 10 minutes before serving warm with whipped cream or a scoop of vanilla ice cream.