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Easy Cosmic Brownie Cookies

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These Easy Cosmic Brownie Cookies are the homemade cookie version of the store-bought Cosmic Brownie treat! They start with a brownie mix and end with the same rainbow chips you know and love.  You need these cookies!

A dozen cosmic brownie cookies on a cooling rack.
Table of Contents

I started these delicious Cosmic Brownie Cookies with a brownie mix for a rich chocolate flavor that is perfect for chocolate lovers. Being able to turn a boxed brownie mix into fudgy brownie cookies is such a time saving way to bake.

A simple frosting and rainbow chips from the sprinkle section of the grocery store are the only other elements needed to complete these amazing cookies.

They come together quickly and can be served warm or chilled, depending on your personal preference. 

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What goes into this Recipe

Ingredients needed to make cosmic brownie cookies with a brownie mix.
  • Brownie Mix- The perfect cookie base for a soft and delicious brownie cookie.  See this Double Dark Chocolate Chip Cookie recipe for another fun option.
  • Flour- Adding a bit of flour to the dry brownie mix will give a cookie a bit more body.
  • Powdered Sugar- The perfect sugar for any kind of frosting because of its soft texture.
  • Cocoa Powder- Added to give the frosting a wonderful chocolate flavor.
  • Heavy Cream- Added to the frosting to help thin it and give it a wonderful flavor.
  • Rainbow-Coated Chocolate Chips- If you can’t find the rainbow candy-coated chocolate chips in the baking aisle, top the chocolate brownie cookies with mini M&M’s, semi-sweet chocolate chips or milk chocolate chips.

See recipe card for full information on ingredients and quantities.

Variations and Substitutions

  • Replace the rainbow-coated mini chips with colorful mini M&M’s. Press a few M&M’s onto the frosting for a pop of color and extra chocolate crunch.
  • Mix creamy peanut butter into the frosting for a delightful peanut butter-chocolate combo. Garnish with chopped peanuts or peanut butter chips.
  • Drizzle warm caramel sauce over the cookies after frosting for an extra layer of gooey sweetness.
  • Incorporate chopped nuts and mini marshmallows into the brownie batter. After frosting, add more nuts and marshmallows for that classic rocky road appeal.

How to make Cosmic Brownie Cookies with a Brownie Mix

  1. To get a little extra structure to the cookie and be sure that they turned out soft and chewy, I added 3 tablespoons of flour to the brownie mix.  Use a whisk to mix them together and take out any lumps.  Mix the dough by hand {or with a hand held mixer} until everything is well combined {the dough will be pretty thick}. 
  2. Use a 1/4 measuring cup {or large cookie dough scoop} to measure out cookie dough mounds.  This will ensure that all of the cookies are the same size and they bake up nicely.  Place 6 cookie dough balls at a time onto a silicone mat {or parchment paper} covered cookie sheet.
Steps 1 & 2 of making Cosmic Brownie Cookies. 1, making the dough. 2, forming the cookies.
  1. Bake cookies for 11-13 minutes or until the edges are set.  The middle will still be a little soft but that’s alright.  Remove them from the oven and let them cool on the baking sheet.  The most important thing to remember is not to over-bake the cookies. They are done when the edges of the cookies are set.
  2. These sweet little rainbow chips can be found by the sprinkles in the cake section of the grocery store.
Steps 3 & 4 of making Cosmic Brownie Cookies. 3, baking the cookies. 4, gathering the sprinkles.
  1. The frosting is made with butter, cocoa, powdered sugar, heavy cream and vanilla.  I used a hand held mixer to get everything incorporated well and smooth.  Once the chocolate cookies are just cooled, begin to take a teaspoon {or so} of the frosting and spread it on each cookie with an offset spatula.  Then liberally sprinkle the top of each cookie with the rainbow chips.
  2. The very best part is the first bite!  Look at the center of that baby.  Just like Little Debbie cosmic brownies but in a cookie form!
Steps 5 & 6 of making Cosmic Brownie Cookies. 5, frost the cookies. 6, a cookie broke in half showing the fudgy middle.

Expert Tips

  1. Use a 1/4 measuring cup {or large cookie scoop} to measure out the cookie dough.  This will ensure that all of the cookies are the same size and that they will bake evenly.  This will also give you nice large cookies.
  2. Don’t over bake the cookies.  Pull them from the oven once the sides are set and the middle is cooked but not completely done.  If you bake the cookies too long, the brownie mix cookies will be dry instead of fudgy cookies.
  3. Allow the baked cookies to cool on the baking sheet.  The residual heat from the baking sheet will continue to slightly bake the cookies and set them up perfectly.
  4. Add the frosting to the cookies once they are slightly cooled but not all of the way.  In order to get the glossy frosting that almost melts into the cookie, the cookie will need to be slightly warm.
  5. Sprinkle with rainbow sprinkles while the frosting is still wet.  If you wait too long the frosting will set up and the sprinkles will not stick.

Storing and Freezing

Store: The best way to store Cosmic Brownie Cookies is in an airtight container either at room temperature or in the refrigerator.  This will depend on whether you prefer eating them chilled or at room temp.

The cookies will last a day or two longer in the refrigerator.

Freeze: These brownie cookies can be frozen for up to 3 months as long as they have been stored in a freezer-safe container.

Recipe FAQs

How do you serve these cookies?

How you serve the Easy Cosmic Brownie Cookies is a personal preference.  I prefer mine warm right after they have been frosting but my family would rather they chill in the refrigerator for an hour or two.

Are they like Crumbl Cosmic Brownie Cookies?

Yes, they are a wonderful copycat crumbl cookie recipe.   These fudgy cosmic brownie cookies are very large in size, covered in chocolate frosting and topped with rainbow chips.

Can I bake smaller cookies?

Absolutely!  Use a medium cookie scoop and bake for 9-11 minutes.  Frost and store as the recipe directs.  You should get between 20-22 smaller cookies.

How do I get perfectly round cookies?

There are a few ways to ensure that you get nice round cookies.  First of all, either use a cookie scoop or roll the cookie dough in your hand and create a round cookie mound.

You can also use a round cookie cutter that is a bit larger than the baked cookie.  While the cookies are still warm, place the cookie cutter over the cookies and move the cutter in a circular motion.  This will help to remove any imperfections and give you a nice round cookie.

A cosmic brownie cookie broke in half and showing the fudgy middle.

Do you love brownies?  Try these easy recipes!!

Did you try this recipe?
Leave a ⭐️ review below and tag @practicallyhomemade on Pinterest!

A dozen cosmic brownies on a cooling rack.

Easy Cosmic Brownie Cookies

A boxed brownie mix is transformed into a delicious and easy Cosmic Brownie Cookie that will remind you of the ones you love from your childhood.
Course: Dessert
Cuisine: American
Prep Time: 10 minutes
Cook Time: 25 minutes
Total Time: 35 minutes
Servings: 12 cookies
Calories: 422kcal
4.46 from 11 votes
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Ingredients

Brownie Cookie

  • 1 box dry brownie mix
  • 3 tbsp flour
  • 2 eggs
  • 1/4 cup vegetable oil

Chocolate Frosting

  • 1/2 cup butter {softened}
  • 2 cups powdered sugar
  • 1/2 cup cocoa powder
  • 1/3 cup heavy cream
  • 1/2 tsp vanilla

Assembly

  • Rainbow-Coated Chocolate Chips

Instructions

Cookies

  • Preheat the oven to 350°.  Combine the brownie mix and flour in a bowl and whisk until the ingredients are incorporated and any lumps are removed.  In a separate bowl combine the eggs and oil, whisk until the ingredients are combined and add it to the dry ingredients.  Using a wooden spoon {or hand held mixer}, stir the ingredients together until everything is well combined and thick.  Use a ¼ measuring cup to measure cookie dough mounds. Form the dough into round discs.  Bake 6 at a time for 11-13 minutes or until the edges are set, they will appear to be a little undercooked but that is alright.  Remove cookies from the oven and let them cool on the cookie sheet.

Frosting

  • Add the frosting ingredients to a large bowl and combine with an electric mixer {I used a hand held mixer} until the frosting is totally combined and smooth.  Add additional heavy cream if the frosting is too thick.

Assembly

  • Once the cookies are cooled {or almost completely} begin frosting the top of each cookie with a teaspoon of frosting and sprinkle with mini chips.
  • Store leftovers in an airtight container at room temperature for 3 days or the refrigerator for 4-5 days.

Video

Notes

  • Don’t over bake the cookies.  Pull them from the oven once the sides are set and the middle is cooked but not completely done.  If you bake the cookies too long, the brownie mix cookies will be dry instead of fudgy.
  • Allow the baked cookies to cool on the baking sheet. The residual heat from the baking sheet will continue to slightly bake the cookies and set them up perfectly.
  • Add the frosting to the cookies once they are slightly cooled but not all of the way.  In order to get the glossy frosting that almost melts into the cookie, the cookie will need to be slightly warm.
  • Sprinkle with rainbow sprinkles while the frosting is still wet.  If you wait too long the frosting will set up and the sprinkles will not stick.

Nutrition

Serving: 1cookie | Calories: 422kcal | Carbohydrates: 57g | Protein: 4g | Fat: 21g | Saturated Fat: 9g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 7g | Trans Fat: 0.3g | Cholesterol: 55mg | Sodium: 198mg | Potassium: 76mg | Fiber: 1g | Sugar: 41g | Vitamin A: 373IU | Vitamin C: 0.04mg | Calcium: 16mg | Iron: 2mg
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