Preheat your oven to 350 degrees and grease a 9x13 baking dish.
Spread half of the mini peanut butter cups evenly across the bottom of the baking dish. Sprinkle the dry chocolate cake mix over the top, spreading it into an even layer. Drizzle the melted peanut butter over the cake mix, followed by the evaporated milk. Scatter the remaining peanut butter cups on top. Drizzle the melted butter evenly over the entire dish.
Bake for 35-40 minutes, or until the top is set and the edges are bubbly.
Allow the dump cake to cool for 10-15 minutes before serving. Top with whipped cream, chopped peanuts or a drizzle of chocolate syrup, if desired.
For extra gooeyness, add an extra handful of peanut butter cups on top after baking.
Serve warm with a scoop of vanilla ice cream for a truly indulgent treat.