Preheat the oven to 350F. Line 2 large baking trays with silpat baking mats or parchment paper.
Add the peanut butter, eggs, and oil to a large bowl. Use a handheld electric mixer to beat until well-combined. Add the cake mix, and beat until it forms a thick cookie dough (see Notes below).
To shape the cookies, roll about 2 tablespoons of dough per cookie into a ball. Arrange the balls on the prepared baking sheets, leaving a couple inches between each dough ball. TIP - I used a slightly heaping 1.5-tablespoon scoop to easily measure out the dough for about 2 tablespoons for each cookie.
Use a fork to make a cross-hatch pattern on the top of each cookie, slightly flattening the cookies as you do so.
Bake until the cookies are golden along the outside and on the bottom, about 12 to 15 minutes, rotating the trays once halfway through.
Let the cookies cool completely before removing them from the trays.
Notes
You will need a standard-size (15.25 ounce) box of yellow cake mix, the kind that calls for oil and eggs on the back. Please use the ingredients listed to make these cookies, not the ingredients on the back of the box.
**This cookie dough is thick and crumbly. It will look like there’s absolutely no way you’ll be able to roll it into balls, but trust me – it rolls into balls perfectly! Just make sure to mix the dough with a handheld electric mixer until it’s well-combined and crumbly.
To freeze your cookie dough, roll them into balls and place on a parchment paper lined baking sheet. Flash freeze until the cookie dough balls are solid. Place them in a large Ziploc bag and store in the freezer for 1-2 months. Flash freezing the cookie balls will help them not stick together. To bake, remove from freezer and allow to thaw for 5-10 minutes or as the oven heats up. Follow the same baking instructions listed in the recipe card below.
Store these peanut butter cake mix cookies in an air-tight container at room temperature for 5-6 days.