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Cosmic Brownie Cookies – soft, fudgy chocolate cookie base topped with a rich and decadent homemade chocolate buttercream with fun rainbow chips. It’s nostalgia in a cookie!
Looking for an out-of-this-world dessert? Look no further than these Cosmic Brownie Cookies! These soft, fudgy cookies are loaded with chocolate flavor and topped with a delicious chocolate buttercream.
They’re inspired by Little Debbie’s famous cosmic brownies, but even better (like, way better). I’ve made homemade Cosmic Brownies and Cosmic Brownie Hot Chocolate Bombs, Cosmic Brownie Pie, and now turned them into cookie form.
These cookies are perfect for parties, just because, or any special occasion. Let’s get baking!
Why you’ll love this Cosmic Brownie Cookie Recipe
- Chocolate lovers unite! These cookies are for you if you’re a chocolate lover like me, and the idea of chocolate on chocolate on chocolate has you excited.
- These cookies are incredibly easy to make and require basic pantry ingredients. You probably have most of the ingredients on hand already!
- The cookie base is rich, fudgy, gooey perfection. They’re also BIG and heavy and perfect for sharing.
- The combination of flavors and textures in these Cosmic Brownie Cookies is out of this world.
- These cookies are sure to be a hit with everyone, adults and kids alike!
Tools you’ll need
- Mixing Bowls – I like these with the grippy bottoms.
- Hand Mixer – Or stand mixer, but I use my hand mixer way more often.
- Silicone Spatulas – I use these for everything in the kitchen.
- Rainbow Chips – These cute little chips can be hard to find at the market, but you can easily order them, or I found mine at Hobby Lobby.
Ingredients for Cosmic Brownie Cookies
Below is a list of ingredients you’ll need to gather to make these cookies. Scroll all the way down for the full recipe card
Brownie Cookie Base with Cocoa Powder
- Butter – Unsalted butter at room temperature.
- Sugars – You’ll mix brown sugar and white sugar which makes for a chewy cookie.
- Egg – One large egg.
- Vanilla Extract – I know vanilla extract is pricey but it is so much better than imitation. Or, you can make your own.
- Cocoa Powder – Unsweetened cocoa powder. I use Hershey’s.
- Flour – All purpose white flour is what I’ve tested with.
- Salt – For balance and it intensifies the chocolate.
- Baking Powder – Helps the cookies to rise.
Chocolate Buttercream Cookie Topping
- Baking Chocolate – I used Ghirardelli 100% unsweetened baking chocolate.
- Butter– I like to use salted butter in my buttercreams for balance, but you can use unsalted. Make sure it is at room temperature.
- Vanilla– Again, I know it is pricey, but you’ll get the best flavor from vanilla extract and not imitation. I pick it up at Sam’s Club or Costco in bulk.
- Powdered Sugar – Sometimes called confectioners’ sugar or icing sugar.
- Milk – I used 2% milk.
How to make Cosmic Brownie Cookies
This section shows you how to make this recipe, with process photos showing the steps to help you visualize it. For full instructions, including amounts and temperatures, see the recipe card below.
- STEP ONE: Make the chocolate cookie dough. First, cream together the softened butter and sugars. Once fluffy, beat in the egg, vanilla, and cocoa powder until fully combined. Then, add in the flour, baking powder, and salt and mix until just combined. The dough will be very crumbly but when pressed together, it will hold its shape.
Divide the dough into six equal portions and roll into balls (they will be very large). Place them onto a baking sheet lined with parchment paper or a silicone mat, cover with plastic wrap, and chill for at least 30 minutes.
- STEP TWO: Make the chocolate buttercream. While the dough is chilling, make the chocolate buttercream by melting the chocolate in a microwave safe bowl and letting cool for approximately 5 minutes. Then, add in the sugar, butter, and vanilla, mixing until well combined. Stream in the milk while mixing until you get the desired consistency. Transfer the frosting to either a piping bag fit with a large, round tip, or put it into a large zip top bag and snip the tip.
- STEP THREE: Bake the cookies. After the cookies have chilled, bake them in a 350° preheated oven for 15-18 minutes. They will not spread much and you want the edges to be just golden. I pressed mine down a bit with a spatula as they came out of the oven. Let cool before frosting.
- STEP FOUR: Assemble the cookies. Once cooled, pipe the frosting onto the cookies in a swirl and top with rainbow chips. Alternatively, you can use an offset spatula (or a knife) to simply frost the cookies.
Tips and Suggestions
- You can use a zip top bag with the tip cut off if you don’t have a piping bag. Or, just frost the cookies with a knife.
- You can order the rainbow chips from Amazon, but I have found them at craft stores(I got mine at Hobby Lobby).
- You must refrigerate the cookies before baking to keep them nice and tall and chewy.
- Gently press the cookies down with a spatula when they come out of the oven if they don’t spread enough.
- You can add some rainbow chips or regular chocolate chips to the dough for an extra dose of chocolate.
- This recipe makes 6 LARGE cookies. They’re big enough to share. You can either double the recipe to make more, or just divide the dough into smaller portions.
- If you’re going into chocolate overload, try using a vanilla buttercream instead.
How To Store Soft Baked Cookies With Icing
Store your cookies in an airtight container at room temperature. They will stay fresh for up to three days…if they last that long!
You’ll want to avoid stacking them if possible. If you just can’t avoid it, then you’ll want to put a sheet of parchment paper in between each layer. The tops will flatten if they’re stored together, so it’s best to store them separately.
If you have any leftover chocolate buttercream, it can be stored in an airtight container in the refrigerator for up to a week. You’ll want to remove the icing from the fridge about 30-45 minutes before using, so it has time to soften to room temperature.
Can I freeze the cookie dough?
If you have made the dough and portioned it out into balls on a baking sheet, then you can easily freeze the cookie dough balls in an airtight container. Once they are frozen, remove them from the freezer and let them thaw on a baking sheet at room temperature. Then bake according to the recipe directions!
You can also pre-bake your cookies and then freeze them if you prefer that method. Just make sure to freeze them in a single layer on the baking sheet, then transfer them to an airtight container. Then just thaw at room temperature before icing!
Cosmic Brownies Cookies FAQs
Can I leave out the cocoa powder from the cookies to make a vanilla base?
Yes! If you want to make some chocolate and some vanilla, all you have to do is separate the dough into two equal portions before adding the cocoa powder. Then add in half the cocoa powder for one portion and continue with the recipe!
Can I use a different type of frosting or glaze?
If you want to try something a little different, try using a chocolate glaze instead of using chocolate buttercream. Just mix together ¼ cup of cocoa powder, ½ cup of hot water, and one cup of sugar. Heat this mixture in the microwave for about 30 seconds, then let it cool for about 15 minutes before using it as a glaze.
You can also add some peppermint extract or vanilla extract to change up the flavor!
Can I use a different type of chocolate in the frosting?
If you want to try something different, try semisweet or milk chocolate instead of using unsweetened baking chocolate. Just make sure that the total amount of chocolate equals 2 ounces. Depending on how sweet your chocolate is, you will likely need to decrease the amount of sugar or it will be overwhelmingly sweet.
What do I do if I can’t find the rainbow chips?
You likely won’t be able to find the rainbow chips at your regular market (at least mine didn’t have them) but you can easily replace them with mini M&Ms if you want to keep the color but don’t want to buy the chips online or search for them in stores.
You could also use mini chocolate chips, chopped-up Hershey’s kisses, or really any other small chocolate-looking candy.
Cosmic Brownie Cookie Recipe
Need more cookie recipes? Try these:
Olive Oil & Sea Salt Brownie Cookies
Double Chocolate M&M Cookies
Chocolate Shortbread Cookies
Click here for my entire collection of cookie recipes.
Cosmic Brownie Cookies
Ingredients
For the cookies
- ½ cup unsalted butter softened to room temperature
- ¾ cup light brown sugar
- ¼ cup granulated white sugar
- 1 large egg
- 1 teaspoon vanilla extract
- ¼ cup unsweetened cocoa powder
- 2 cups all purpose flour
- ½ teaspoon salt
- ½ teaspoon baking powder
For the chocolate buttercream
- 2 ounces unsweetened baking chocolate
- 4 Tablespoons butter softened to room temperature
- 1 teaspoon vanilla extract
- 3 cups powdered sugar
- 3.5 Tablespoons milk I used 2%
- 1 pinch salt optional
- Rainbow candy chips
Instructions
To make the chocolate cookies
- In a large bowl cream together the butter and both sugars until fluffy.½ cup unsalted butter, ¾ cup light brown sugar, ¼ cup granulated white sugar
- Beat in the egg, vanilla extract, and cocoa powder.1 large egg, 1 teaspoon vanilla extract, ¼ cup unsweetened cocoa powder
- Add in the flour, salt, and baking powder. Mix until just combined. It will be very crumbly but should easily press together.2 cups all purpose flour, ½ teaspoon salt, ½ teaspoon baking powder
- Divide the dough into 6 equal portions and form each portion into a large ball.
- Place the balls onto a baking sheet lined with parchment paper or a silicone baking mat. Loosely cover with plastic wrap and refrigerate for at least 30 minutes.
- While chilling, I suggest making the buttercream and preheating the oven to 350°.
- Once chilled, bake the cookies for 15-18 minutes. The edges should be just golden. If you over-bake, you'll lose the chewiness. Press down with the back of a spatula if you prefer flatter cookies.
- Cool 5 minutes and then transfer to a rack to cool completely.
To make the chocolate buttercream
- To a medium microwave safe bowl, add the chocolate and heat in 30 second increments, stirring in between, until melted and smooth. Cool 5 minutes.2 ounces unsweetened baking chocolate
- Once cooled, add the softened butter, vanilla extract, and powdered sugar. Use a hand mixer to beat until smooth.4 Tablespoons butter, 1 teaspoon vanilla extract, 3 cups powdered sugar
- Gradually add the milk while beating with the mixer until the desired consistency is reached.3.5 Tablespoons milk
- Taste and adjust to your preference. I add an additional pinch of salt because I don't like overly sweet buttercream.1 pinch salt
- Transfer the frosting to either a piping bag fitted with a large, round tip OR place it into a large zip top bag and snip the tip.
Assemble
- Pipe the buttercream into a swirl on top of the cooled cookies. (alternatively, you can simply frost them with an offset spatula).
- Sprinkle with rainbow chips and enjoy!Rainbow candy chips
Notes
- You can use a zip top bag with the tip cut off if you don’t have a piping bag. Or, just frost the cookies with a knife.
- You can find the rainbow chips on Amazon, but I have found them at craft stores(I got mine at Hobby Lobby).
- You must refrigerate the cookies before baking to keep them nice and tall and chewy.
- Gently press the cookies down with a spatula when they come out of the oven if they don’t spread enough.
- You can add some rainbow chips or regular chocolate chips to the dough for an extra dose of chocolate.
- This recipe makes 6 LARGE cookies. They’re big enough to share. You can either double the recipe to make more, or just divide the dough into smaller portions.
- Store leftovers in an airtight container at room temperature for up to 3 days.
Nutrition
Nutritional information is an estimate and provided to you as a courtesy. You should calculate the nutritional information with the actual ingredients used in your recipe using your preferred nutrition calculator.
