Instructions:
- Preheat oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish.
- Evenly sprinkle the entire dry cake mix across the bottom of the prepared dish.
- Sprinkle both types of chocolate chips (and nuts, if using) evenly over the dry cake mix layer.
- Slowly drizzle the entire can of sweetened condensed milk over the chip layer, aiming for even distribution.
- Whisk together the 1 cup of water and the 1 cup of melted butter until just combined. Gently pour this slurry mixture over the top surface of the ingredients.
- Bake for 45 to 55 minutes. The edges should look set, and the top should be bubbly.
- Check doneness: A knife inserted near the center may come out gooey, but the surrounding edges should be firm.
- Allow the Chocolate Dump Cake to cool for at least 15 minutes before scooping and serving warm.