Cosmic Brownie Cookies

Cosmic Brownie Cookies are a nostalgic twist on the iconic childhood treat. These soft, chewy cookies are rich with chocolate flavor, topped with a smooth fudge frosting and finished with colorful rainbow candy-coated chips. Every bite takes me back to school lunchboxes and convenience store snacks—but made fresh and better at home.

Why You’ll Love This Recipe

I love these cookies because they combine the best parts of brownies and cookies into one easy dessert. They have that dense, fudgy center I expect from brownies, but with the portability and portion control of a cookie. The glossy chocolate frosting and bright sprinkles on top add fun and sweetness that makes them feel playful and special—ideal for parties, bake sales, or just satisfying a chocolate craving.

Ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

• Unsalted butter

• Brown sugar

• Granulated sugar

• Eggs

• Vanilla extract

• All-purpose flour

• Unsweetened cocoa powder

• Baking soda

• Salt

• Semi-sweet chocolate chips (optional for extra richness)

• Heavy cream

• Powdered sugar

• Chocolate chips or chopped chocolate (for frosting)

• Rainbow candy-coated chocolate chips (like mini M&Ms or rainbow chips)

Directions

1. I preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

2. In a mixing bowl, I cream together the butter, brown sugar, and granulated sugar until light and fluffy.

3. I beat in the eggs and vanilla extract until well combined.

4. In a separate bowl, I whisk together the flour, cocoa powder, baking soda, and salt.

5. I gradually mix the dry ingredients into the wet mixture until a thick dough forms. If I want extra chocolate richness, I stir in some semi-sweet chocolate chips.

6. Using a cookie scoop or spoon, I portion the dough into balls and place them on the baking sheet, leaving some space between each.

7. I bake the cookies for 8–10 minutes, just until the edges are set but the centers are soft. I let them cool completely on a wire rack.

8. While the cookies cool, I make the frosting by gently melting chocolate with butter and a splash of heavy cream, then stirring in powdered sugar until smooth and glossy.

9. I spread the frosting over each cooled cookie and immediately top with rainbow chips before it sets.

Servings and timing

This recipe makes about 18 cookies, depending on size. I can usually prep and bake them in under 40 minutes—about 20 minutes for mixing and forming, 10 minutes for baking, and a bit of cooling and frosting time.

Variations

Sometimes I use white chocolate chips in the dough for a contrast in flavor. If I want a festive look, I swap out the rainbow chips for holiday-colored sprinkles. For a mocha twist, I add a teaspoon of espresso powder to the cookie dough. And if I’m in the mood for a stuffed cookie, I press a square of chocolate or a dollop of Nutella into the center before baking.

Storage/Reheating

I store these cookies in an airtight container at room temperature for up to 4 days. If it’s warm out, I refrigerate them to keep the frosting firm. They also freeze well—I just layer them with parchment paper and thaw at room temp. I don’t usually reheat them, but if I want a warm cookie, a quick 5–7 seconds in the microwave does the trick.

FAQs

Do I have to frost the cookies?

Not at all. The cookies are delicious on their own, but the frosting and rainbow chips give them that classic “cosmic brownie” look and taste.

Can I use store-bought frosting?

Yes, I can use a good-quality chocolate frosting from the store if I’m short on time. Just make sure the cookies are completely cool before frosting.

How do I keep the cookies soft?

I make sure not to overbake them—the centers should still look slightly underdone when I take them out. I also store them in an airtight container with a slice of bread to keep them soft.

Can I make the dough ahead of time?

Absolutely. I refrigerate the dough for up to 48 hours, then let it sit at room temperature for 10 minutes before baking.

What kind of rainbow chips should I use?

I like using candy-coated chocolate chips or mini rainbow chips for the classic look. Mini M&Ms also work great for a colorful crunch.

Conclusion

Cosmic Brownie Cookies are a fun, nostalgic treat that brings a bakery-quality upgrade to a childhood favorite. I love how simple they are to make, and the combination of fudgy cookie, rich frosting, and colorful sprinkles never fails to impress. Whether I’m baking for kids or grown-ups, these cookies always bring smiles.