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Cake Batter Monster Cookie Sandwiches

Funfetti meets oatmeal cookies! These Cake Batter Monster Cookie Sandwiches are chewy oatmeal cookies made with vanilla cake mix and loaded with MnMs, chocolate chips and sprinkles. Finish them off with some vanilla buttercream for the perfect cookie sandwich.

Stacked oatmeal cookie sandwiches

Funfetti Oatmeal Monster Cookies

These Cake Batter Monster Cookie Sandwiches are so fun! It’s my favorite oatmeal cookies but made with cake mix, sprinkles, MnMs and white chocolate chips. They’re chunky and downright delicious. 

Over the years, I’ve perfected my oatmeal cookies. Equal parts granulated and brown sugar makes them soft & chewy. With the addition of cake mix, these are extra soft and tender. 

Since I like to go a little overboard with my desserts, I chose to make these cookie sandwiches. This is totally optional, but let’s face the facts, you’re going to eat more than one cookie, so why not smoother some vanilla buttercream in between. 

Go ahead and take a nice big bite and let that buttercream smoosh out of the sides, extra napkins are required. 

A monster cookie leaning up against a milk glass

It’s All About The Cake Mix

You’ll notice this recipe calls for 1/4 cup of cake mix. That’s dry cake mix, right from the box. You can use a vanilla, yellow or white cake mix but I think the vanilla or yellow have better flavor. 

The cake mix helps make these really tender but also it’s where the flavor comes from. After all, these are cake batter oatmeal cookies! 

How to Make Monster Cookies

  • Soften the cold butter in the microwave is for 10-12 second
  • Cream the butter & sugars until fluffy 
  • Add the egg and vanilla 
  • Combine and add the dry ingredients 
  • Add the MnM, chocolate chips & sprinkles
  • Bake for 13-15 minutes. You will pull them out of the oven before the centers are fully baked through. Leave them on your baking sheet for several minutes.

These cookies shape the best when they’re full of MnMs and chocolate chips, so if you find the bottom of your mixing bowl is really doughy, go ahead and throw some more of the good stuff in there! 

A stack of three cookie sandwiches with vanilla buttercream, the one on top had a bite taken out of it

3 Tips for Perfect Cookies

  • Line your baking sheets with silicone baking mats. These are game changers for cookie baking. It helps the cookies from spreading and burning on the bottom or edges.
  • To ensure your cookies bake evenly, use a cookie scoop to keep the cookies are the same size.
  • Right when you pull them out of the oven, take an angled spatula, a cookie spatula and any flat surface and push the edges of the cookies back towards the center of the cookie. This makes a nice round shape and also helps keep the center nice and puffy. It also works with a round cookie cutter. 
an overhead shot of MnM oatmeal cookies

Frost These to Make Cookie Sandwiches

It’s best to let the cookies cool completely before adding the frosting, or you might have quite the mess on your hands.

I like to use a piping bag or ziplock bag to swirl my frosting and I love a french star tip because it gives the frosting a little bit of texture around the outside edge. 

  • Find two cookies that are the similar in size. 
  • Fill your piping bag and then cut off the tip of 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 more sprinkles
vanilla buttercream swirled on an oatmeal cookie

How to Store Baked Cookies

Store them in an airtight container or in a Ziploc bag whether they’re frosted or not. 

To freeze these, I prefer to place them in an airtight container and I recommend freezing them without the frosting. Thaw completely before adding the frosting. 

A giant stack of MnM oatmeal cookies

More Oatmeal Cookie Recipes You’ll Love

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Stacked oatmeal cookie sandwiches

Cake Batter Monster Cookie Sandwiches

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  • Author: Julianne Dell
  • Prep Time: 15 minutes
  • Cook Time: 14 minutes
  • Total Time: 29 minutes
  • Yield: 8 sandwiches – 16 cookies
  • Category: Cookies
  • Method: Baked
  • Cuisine: American


Cake Batter Monster Cookies are chewy oatmeal cookies with vanilla cake mix and a layer of creamy vanilla frosting. The cookies are filled with MnMs, sprinkles and white chocolate chips.


  • 1/2 cup (113g) unsalted butter, cold
  • 1/2 cup (95g) granulated sugar
  • 1/2 cup (110g) light brown sugar
  • 1 large egg
  • 1 tablespoon (15ml) pure vanilla extract
  • 1 cup (140g) all purpose flour
  • 1/4 cup (35g) vanilla cake mix, dry
  • 1 cup (80g) rolled oats
  • 1/2 teaspoon baking soda
  • 1/2 teaspoon salt
  • 1/2 cup (90g) white chocolate chips
  • 1/2 cup MnMs
  • 1/4 cup sprinkles

For the frosting

  • 3/4 cup (170g) unsalted butter, cold
  • 2 1/2 cups (325g) powdered sugar
  • 2 teaspoons (10ml) pure vanilla extract
  • 1 tablespoon (15ml) milk or heavy cream
  • Additional Sprinkles for garnish


  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.


  • Cake mix: Vanilla, yellow or white cake mix will work.
  • Oats: I prefer to use rolled oats but quick oats will also work
  • Storage: Keep these stored in an airtight container or Ziploc bag
  • When your cookies come out of the oven and they do spread or are misshaped, take a flat edge, such as a knife and press the edges of the cookie back towards the middle of the cookie, shaping it into a circle.
  • This recipe can easily be doubled. As written it makes 16 cookies (or 8 cookie sandwiches)


  • Serving Size: 1 Cookie Sandwich
  • Calories: 743
  • Sugar: 78g
  • Fat: 36g
  • Carbohydrates: 99g
  • Fiber: 1g
  • Protein: 5g
  • Cholesterol: 104mg

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27 thoughts on “Cake Batter Monster Cookie Sandwiches”

  1. Avatar photo
    Robin Smalley

    I have looked all over for the bday cake mms (even crossing the border to the states!) and have had no luck!
    What would you substitute them with?

  2. These look divine and I plan to make them for a Labor Day Weekend BBQ…but I have a potentially stupid question: are there oats in these cookies? Because the description mentions oatmeal cookies, but I do not see oats in the ingredient list. I want to make sure I’m not doing something wrong… Thank you!!!

    1. Julianne - Beyond Frosting
      Beyond Frosting

      Oh my word! Thank you Sarah! Yes, there are quick oats in this recipe and it appears they were missing from the recipe. Thank you for letting me know!

  3. These look great and perfect for a school birthday treat! I am curious though… how necessary is the butter extract? Does it make a huge difference in flavor? Thanks for sharing!

  4. Avatar photo

    I am not sure how your cookies came out looking like that. I followed the recipe exactly and by using 2T of dough the cookies spread like crazy and were brittle. I cut back to using my normal cookie scoop and they still spread out almost flat.

    I love the idea but not sure I will be making again.

    1. Julianne - Beyond Frosting
      Beyond Frosting

      Hi there, I am sorry you didn’t have success with these. Unfortunately, as I mentioned in my post, that silicone mats were very helpful for me in baking these. Pans and location in the oven can factor in to how a cookie bakes as well. I have a Pampered Chef and OXO Cookie Scoop that are each 2 tbsp, which is what I use for my large cookies. If you bake a test batch first, and your cookies are spreading, I would suggest to refrigerate the dough for 30 minutes. I know it’s annoying but it can help with the spreading.

  5. Avatar photo
    Julie @ Julie's Eats & Treats

    Mmmmm I’m all about eating two cookies instead of one especially when they are held together but a bunch of frosting!!!

  6. Avatar photo
    Gayle @ Pumpkin 'N Spice

    I know what you mean about back to school traffic! Luckily it doesn’t make my commute too much longer, but I do notice more people on the roads! These sandwiches look like the perfect school transition dessert! So pretty and love the flavors! Pinned!

    1. Julianne - Beyond Frosting
      Beyond Frosting

      Thanks Gayle! At least I don’t have to wait in the school pick up line for several more years! LOL

  7. Avatar photo
    Jocelyn (Grandbaby cakes)

    Oh wow these cookies are fantastic!! I will email you my address so you can ship them.

  8. Avatar photo
    Heather @ Shards of Lavender

    A cake batter monster cookie? Two of my favorite flavors combined~ thank you! Interesting the difference in how the cookies baked up with the Silpat… I love mine and don’t ever bake cookies with out them!

  9. These cookies sound yummy, a definite hit with the kids! You may have gotten the total time wrong, 60 hours?

  10. My Silpat mats are among my most prized possessions. I lost them for about 5 minutes last month and I went completely ballistic!
    These look so great. If you debut a monster cookie, this is how it’s done!