Cookie Monster Sheet Cake
August 19, 2026
A bright blue chocolate chip cake covered in cookie dough buttercream and mini chocolate chip cookies!
This Cookie Monster Sheet Cake has a soft vanilla cake base filled with mini chocolate chips and topped with cookie dough buttercream. The bright blue cake, mini chocolate chip cookies, and sprinkles give it the Cookie Monster look, while the vanilla and chocolate chip combo keeps the flavor classic and fun.
Flavor Profile
The cake has a sweet vanilla flavor with little bites of chocolate from the mini chips throughout. The cookie dough buttercream adds a buttery vanilla flavor with even more chocolate chips, while the mini cookies on top add a little crunch.
Why You’ll Love This Recipe
- The bright blue vanilla cake is filled with mini chocolate chips in every slice.
- A doctored cake mix keeps the recipe easy while sour cream and butter make it soft and rich.
- Cookie dough buttercream adds even more chocolate chip cookie flavor on top.
- Mini cookies, chocolate chips, and sprinkles make decorating super simple and fun.
- It’s an easy 9×13-inch party cake with no layers or complicated decorating required.
The Twist
The twist is the Cookie Monster theme. Bright blue cake, chocolate chip cookies, and blue sprinkles turn a classic vanilla chocolate chip sheet cake into a fun Cookie Monster dessert.
Ingredient Highlights
- Vanilla cake mix: The easy starting point for the cake and gets a little upgrade with milk, sour cream, and melted butter.
- Sour cream: Adds moisture and richness without changing the vanilla flavor.
- Blue food coloring: Gel food coloring will give you a brighter blue without adding too much extra liquid to the batter.
- Mini chocolate chips: Their small size makes them easy to distribute throughout the cake and frosting.
- Heat-treated flour: Gives the buttercream its cookie dough flavor. Make sure the flour is heat-treated before adding it to the frosting.
- Mini chocolate chip cookies: Use your favorite mini cookies to decorate the finished cake.
Cookie Monster Sheet Cake
Ingredients
Cake
- 1 box vanilla cake mix
- 1 cup whole milk
- ½ cup sour cream
- ½ cup salted butter, melted and slightly cooled
- 4 large eggs
- 2 teaspoons vanilla extract
- Blue food coloring
- 1 cup mini chocolate chips
- 1 tablespoon all-purpose flour
Cookie Dough Buttercream
- 2 sticks salted butter, softened
- 3½ cups powdered sugar
- ½ cup heat-treated all-purpose flour
- 2 teaspoons vanilla extract
- 3–5 tablespoons heavy cream
- Pinch of salt
- ¾ cup mini chocolate chips
Decorations
- Mini chocolate chip cookies
- Mini chocolate chips
- Blue sprinkles
- Chocolate sprinkles
Instructions
- Preheat the oven according to the temperature listed on the cake mix box. Grease a 9×13-inch baking pan.
- Beat together the cake mix, milk, sour cream, melted butter, eggs, and vanilla until smooth. Add blue food coloring a little at a time until you reach a bright Cookie Monster blue.
- Toss the mini chocolate chips with the flour, then fold them into the batter. Spread the batter evenly in the prepared pan and bake according to the time listed on the cake mix box, or until a toothpick inserted into the center comes out clean. Let the cake cool completely.
- To make the cookie dough buttercream, beat the butter until light and fluffy. Gradually beat in the powdered sugar, heat-treated flour, vanilla, and salt. Add the heavy cream a tablespoon at a time until the frosting is smooth and fluffy. Fold in the mini chocolate chips.
- Spread the buttercream over the cooled cake. Top with mini chocolate chip cookies, extra mini chocolate chips, and a mix of blue and chocolate sprinkles.
FAQ
Can I make this Cookie Monster Sheet Cake ahead of time?
Yes. Bake the cake a day ahead, let it cool completely, and keep it tightly covered. Frost and decorate it before serving.
Why do I need to heat-treat the flour?
Raw flour isn’t intended to be eaten without cooking. Heat-treating it makes it suitable for using in the cookie dough buttercream.
Can I use regular-size chocolate chips?
You can, but mini chocolate chips work better because they spread more evenly throughout the cake and frosting.
What type of blue food coloring works best?
A concentrated gel food coloring is your best bet for getting a bold Cookie Monster blue without thinning out the cake batter.
Do I need to refrigerate the cake?
If you’re serving it the same day, it can stay covered at room temperature for several hours. For longer storage, keep it covered in the refrigerator and bring it closer to room temperature before serving.
Sprinkle of Fun
Make this Cookie Monster Sheet Cake for a Sesame Street party and build the rest of the treats around your favorite characters. It’s such a fun theme for a colorful dessert table!
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