Instructions

1. Preheat the oven to 350° F. Soften the cold butter in the microwave for 10-15 seconds. Combine the softened butter with the brown and granulated sugar. Beat on medium speed until well combined, 2-3 minutes.
2. Next add the egg and vanilla extract and continue beating until well incorporated.
3. In a separate bowl, combine the dry ingredients: flour, cake mix, oats, salt and baking soda. Stir to combine and slowly add the dry ingredients into the dough, mixing on low speed until dough starts to form.
4. Before the dough thickens, add the chocolate chips, MnMs and sprinkles. Beat a couple of times until they start to incorporate.
5. Line a baking sheet with parchment paper or a silicone baking sheet. Scoop the dough using a large cookie scoop and place on a sheet pan, 2 inches apart.
6. Bake for 13-15 minutes. The center of the cookie should be slightly under baked but not too gooey. Allow to cool on the baking sheet for 5-10 minutes before transferring to a wire rack to cool.
7. For the frosting: Cut the butter into smaller pieces. Using the paddle attachment, whip the butter for 5-7 minutes, scraping down the bowl occasionally, beating until the butter is very fluffy.
8. Add the powdered sugar, vanilla extract & heavy cream. Ensure the powdered sugar is well combined, then and whip for 3-4 minutes at high speed.
9. To assemble the cookies, find two cookies that are similar in size. Use a piping bag or Ziploc bag and cut of the tip off the bag, swirl the frosting on one side of the cookie. Place a second cookie on top and gently press down. Then you can roll the edges in additional sprinkles.