Cosmic Brownie Cookies are pure nostalgia baked into cookie form. If you grew up loving those thick, fudgy brownies with the glossy chocolate frosting and rainbow chips, these cookies are going to hit all the right notes. They have soft, chewy centers, crisp edges, and a rich chocolate ganache on top that makes them feel just a little extra special.
These are the kind of cookies that disappear fast. Cosmic Brownie Cookies are perfect for bake sales, parties, or just a random Tuesday when you want a dessert that feels fun without being complicated. The dough comes together quickly, they bake in under ten minutes, and the ganache frosting is simple but dramatic in the best way.
This recipe was inspired by my love of nostalgic desserts with an elevated twist, similar to how I approach sauces and toppings like my Hot Fudge Sauce. Familiar flavors, simple techniques, and results that feel bakery worthy without the stress.
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Chocolate Brownie Cookies Ingredients
This recipe uses mostly straightforward pantry staples, but each ingredient plays an important role in getting that classic Cosmic Brownie flavor and texture.
- Dutch processed cocoa powder: This gives the cookies their deep chocolate flavor and dark color. I like using the Ghirardelli brand because the quality really shows here. Natural cocoa powder will work, but the cookies will be lighter in color and slightly less rich.
- All-purpose flour: Provides structure while still keeping the cookies soft and chewy. If you don't have a kitchen scale, make sure to spoon the flour into your measuring cup (the spoon and level method) so that your cookies aren't too dry.
- Baking soda: Helps the cookies spread just enough and gives them a tender texture.
- Salted butter: Using melted butter keeps the cookies dense and fudgy rather than cakey. Unsalted butter works too, just add a small pinch of salt.
- Granulated sugar and brown sugar: This combination gives you crisp edges from the white sugar and chewiness from the brown sugar.
- Egg and egg yolk: The extra yolk adds richness and keeps the cookies soft.
- Heavy cream and semisweet chocolate chips: These come together to make the silky ganache frosting that really sets these cookies apart. You don't have to make the ganache frosting- the cookies stand alone on their own, but the ganache was a huge hit in our home.
- Rainbow candy coated chips: The signature Cosmic Brownie look and a fun pop of crunch. You can very easily use m&ms if you can't find them in stores. I bought mine on Amazon here.
See my recipe card for quantities and full instructions.
Instructions
- Step 1:Mix The Dough- Start by whisking together the flour, cocoa powder, baking soda, and salt in a medium bowl. In a separate large bowl, stir together the melted butter, granulated sugar, and brown sugar until smooth. Beat in the egg, egg yolk, and vanilla, then stir in the dry ingredients just until a thick chocolate dough forms.
- Step 2: Scoop and Bake: Use a 2 inch cookie scoop to portion the dough onto parchment lined baking sheets, spacing them about two inches apart. Bake at 350°F for 7 to 9 minutes, until the edges are set but the centers are still soft. Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack.
- Step 3: Make the Ganache Frosting: Heat the heavy cream in a small saucepan just until steaming, not boiling. Pour it over the chocolate chips and let it sit for 2 to 3 minutes before whisking until smooth and glossy. Chill the ganache briefly until it thickens to a spreadable consistency.
- Step 4: Frost and Decorate: Once the cookies are completely cool, spread a layer of ganache over each one. Immediately top with rainbow candy coated chips so they stick before the ganache sets. Let the frosting firm up slightly before serving or storing.
Top Tip
Do not over bake these cookies. They should look slightly underdone in the center when you pull them from the oven. They will continue to set as they cool, and this is what keeps them soft and fudgy instead of dry.
Variations
These cookies are easy to customize while keeping that Cosmic Brownie vibe.
- Swap the rainbow chips for holiday colored m&ms or sixlets to make them seasonal.
- Use dark chocolate chips in the ganache for a less sweet, more intense chocolate flavor.
- Add a pinch of flaky sea salt on top of the ganache for a sweet salty contrast.
- Skip the ganache entirely and enjoy them as rich chocolate brownie cookies with chewy centers.
See this pumpkin version of this recipe on my website!
Equipment
You don’t need anything fancy to make these Cosmic Brownies Cookies, just a few basic kitchen tools you probably already have on hand. This setup keeps the process simple from mixing to frosting.
- Two baking sheets: Used to bake the cookies evenly and give them enough space to spread without touching.
- Parchment paper: Prevents sticking and helps the cookies bake evenly without over browning on the bottom.
- Mixing bowls: You will need three bowls total. Two small bowls for the dry ingredients and the ganache and one larger bowl for mixing the dough together.
- Whisk and spatula: The whisk helps evenly combine dry ingredients, while the spatula is perfect for mixing the dough and spreading the ganache.
- Measuring cups and spoons
- Saucepan: Used to gently heat the cream for the ganache without scorching. You can also heat the cream in the microwave using a microwave safe bowl.
- Wire cooling rack: Allows air to circulate so the cookies cool completely before frosting.
Storage
Store Cosmic Brownies Cookies in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 5 days. For longer storage, freeze the cookies without ganache for up to 2 months. Thaw, frost, and decorate when ready to serve.
The ganache may harden in the refrigerator. To reheat, place in a saucepan on the stove for 3-4 minutes or until it's at a spreadable consistency, or microwave for 30 seconds to1 minute.
More Tips
- Let the ganache set: After spreading the chocolate, allow it to cool and firm up slightly before adding rainbow chips. This prevents them from sliding off. If the ganache feels thin, refrigerate it for 10-15 minutes to firm to a spreadable consistency.
- Use high-quality cocoa. Dutch processed cocoa gives the cookies a rich, deep chocolate flavor and that signature “Cosmic Brownie” taste.
- Cool before frosting. Wait until cookies are fully cooled before adding ganache or it will melt right off.
Related
Looking for other recipes like this? Try these:
Cosmic Brownie Cookies
Equipment
- Two baking sheets
- Parchment Paper
- Mixing Bowls
- Whisk and spatula
- Measuring cups and spoons
- Saucepan
- Wire cooling rack
Ingredients
Cookies:
- ½ cup (50 grams) dutch processed cocoa powder
- 1 ½ cups (185 grams) all-purpose flour, spooned and leveled
- 1 teaspoon baking soda
- ½ teaspoon salt
- ½ cup (113 grams) salted butter, melted
- ¾ cup (150 grams) granulated sugar
- ¼ cup (55 grams) brown sugar, packed
- 1 large egg plus 1 egg yolk
- 1 teaspoon vanilla extract
Chocolate Ganache Frosting:
- ¾ cup heavy cream
- 1 cup semisweet chocolate chips
- ½ cup rainbow candy coated chips
Instructions
- Preheat the oven to 350°F and line two baking sheets with parchment paper.
- In a medium sized bowl add flour, cocoa powder, baking soda, and salt and stir to combine. Set aside for now.
- In a large mixing bowl, cream together the butter, granulated sugar, and brown sugar until fully combined.
- Beat in the egg, egg yolk, and vanilla extract until smooth.
- Stir in the flour mixture just until a dough forms.
- Using a 2 inch cookie scoop, drop dough onto the prepared sheets about two inches apart.
- Bake for 7-9 minutes or until the cookies are set around the edges but still soft in the centers. Don’t overcook. Set aside to cool.
- To make frosting, heat heavy cream over medium high heat in a small sauce pan until smoking, but not boiling.
- Immediately pour over chocolate chips. Let sit for 2-3 minutes before whisking. Set in the refrigerator until it cools to a spreadable consistency.
- Spread ganache over each cookie before sprinkling with rainbow candy coated chips.
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