Preheat your oven to 350 degrees F. Line a cookie sheet with parchment paper or silicone mats and set aside.
In a large bowl, add the yellow cake mix, egg, oil, and 3 Tablespoons of water. With a hand mixer on medium, mix until smooth.
15.25 ounce fudge marble cake mix, 1 large egg, 1/3 cup vegetable oil, 4 Tablespoon water
In a small bowl, add the fudge packet and 1 Tablespoon of water and mix until combined with a fork. If yours is too dry, drizzle in a little more water to get it to come together.
Scoop out 2/3 cup of the yellow cake batter and add it to the fudge mixture. Stir to fully combine.
Pour the chocolate chips into the yellow cake batter and stir to distribute.
1 cup chocolate chips
Pour the chocolate batter into the yellow batter and stir gently to swirl them together. Do no over mix – you want to see the swirls.
Use a cookie scoop to portion out cookie balls and place them 1″ apart on the cookie sheet.
Bake for 6 minutes, rotate the pan, then bake for another 6 minutes.
Remove from oven and let cool on the pan.
Video
Notes
Store leftover cookies in an airtight container for up to a week.If you can't find a fudge marble cake mix, do the following:Prepare a 15 oz yellow cake mix according to the package instructions. Once you have the batter, remove 2/3 cup of it & pour it into a small bowl. To the reserved batter, add 2 tablespoons of unsweetened cocoa powder and 1.5 tablespoons of water, mixing until well blended. Resume following the recipe as stated.