Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the chocolate cake mix and milk until well blended and smooth.
Pour half of the chocolate cake batter into a greased 9x13 inch baking dish, spreading it evenly across the bottom.
Evenly distribute the chopped Oreo cookies over the batter, ensuring coverage across the entire layer.
Pour the remaining chocolate cake batter over the Oreo layer, making sure to cover it completely.
Drizzle the sweetened condensed milk over the top of the cake batter, allowing it to seep in.
Pour the melted butter evenly across the surface.
Sprinkle the semi-sweet chocolate chips over the top for an added layer of richness.
Bake in the preheated oven for 30 to 35 minutes, or until the cake is set and a toothpick inserted in the center comes out mostly clean.
Allow the cake to cool for at least 10 minutes before serving. Enjoy warm or at room temperature, perhaps with a scoop of vanilla ice cream.