Step 1

Preheat the oven to 350°F. Grease a 9x13-inch baking pan with non-stick cooking spray.

Step 2

Arrange 18-20 Oreo cookies in a single layer on the bottom of the prepared pan, covering as much surface area as possible.

Step 3

Pour the sweetened condensed milk evenly over the layer of Oreo cookies.

Step 4

Spread the thawed whipped topping over the sweetened condensed milk in an even layer.

Step 5

Sprinkle the dry chocolate fudge cake mix evenly over the whipped topping layer. Use a fork to break up any large lumps in the cake mix.

Step 6

Arrange the butter slices in a single layer on top of the cake mix, covering as much surface area as possible.

Step 7

Roughly chop the remaining 4-6 Oreo cookies and sprinkle them on top of the butter layer.

Step 8

Bake in the preheated oven for 35-40 minutes, until the top is set and the butter has been absorbed into the cake mix.

Step 9

Remove from the oven and let cool for 5-10 minutes. Serve warm, scooping out portions with a large spoon.

Step 10

If desired, top individual servings with a scoop of vanilla ice cream and a drizzle of chocolate syrup. Enjoy!