Step 1: Preheat & Prepare the Pan

• Preheat oven to 350°F (175°C).

• Line a 9×13-inch baking pan with aluminum foil, leaving an overhang on the sides for easy removal.

• Lightly spray the foil with non-stick baking spray.

Step 2: Make the Base

• In a large bowl, mix the cake mix, eggs, and oil until fully combined.

• Press ⅔ of the dough evenly into the bottom of the prepared pan.

• Set the remaining batter aside for later.

Step 3: Prepare the Chocolate Fudge Layer

• In a microwave-safe bowl, combine:

  • 1 can sweetened condensed milk

  • 1 cup chocolate chips

  • ½ stick butter

• Microwave on high for 1 minute. Stir until smooth and well-blended.

Step 4: Assemble

• Pour the chocolate fudge mixture evenly over the cake base.

• Drop small spoonfuls of the remaining batter over the top to create a marbled effect.

Step 5: Bake

• Bake for 20–25 minutes, or until the edges are golden and the center is just set.

• Do not overbake—the center should still be soft and fudgy.

Step 6: Cool & Slice

• Cool completely in the pan.

• Use the foil overhang to lift the bars out.

• Cut into squares or rectangles and serve.