I’ve transformed my childhood favorite—those nostalgic cosmic brownies—into this cookie form: rich, fudgy chocolate cookies topped with silky ganache and colorful sprinkles. It’s everything I love about the original treat, made even better.

Why You’ll Love This Recipe

I love how these cookies hit all the right notes: intense chocolate flavor thanks to dark cocoa powder, a melt-in-your-mouth fudgy center, and the satisfying crunch from the rainbow "cosmic" sprinkles. They’re ideal for dunking in cold milk or bringing to a gathering—they always disappear fast!

Ingredients

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

1 cup salted butter, melted
1 ¼ cups granulated sugar
¾ cup light brown sugar
2 teaspoon vanilla extract
2 eggs, room temperature
1 ⅓ cups all-purpose flour
2 teaspoon corn starch
1 cup cocoa powder (I prefer dark chocolate cocoa powder)
1 teaspoon baking soda
½ teaspoon kosher salt

For the ganache frosting:

8 oz semi-sweet chocolate (bars or chips)
¾ cup heavy cream
½ teaspoon vanilla extract
1 cup cosmic brownie sprinkles

Directions

In a stand mixer, I whisk together the melted butter, sugars, and vanilla for 1 minute. I add eggs and mix until just incorporated.
I add flour, corn starch, cocoa powder, baking soda, and salt. I mix on low until everything is combined.
I scoop about 2–2.5 tablespoons of dough onto parchment-lined baking sheets. I chill them for 30 minutes to prevent spreading.
I preheat the oven to 350 °F. I arrange dough balls 2 inches apart and bake for 9–10 minutes until edges are set. I cool them on the sheet for 3 minutes, then transfer to a wire rack.
While cooling, I make the ganache: I heat cream until simmering, pour it over chopped chocolate, let it sit for 5 minutes. I add vanilla and whisk until smooth. I let it cool 15–30 minutes until spreadable.
Once cookies are cool, I spread about 2–3 tablespoons ganache on each, leaving a small border. I top with sprinkles. I serve immediately or chill to set the ganache.

Servings and timing

This batch yields about 20 cookies.

Prep time: ~10 minutes (plus 30 minutes chill)
Bake time: 9–10 minutes per batch
Ganache set-up: 15–30 minutes cooling before spreading

If someone ever asks, I’d say the total hands-on time is roughly 45 minutes, but I plan ahead for chilling.

Variations

I swap dark cocoa for regular cocoa when I want a milder chocolate flavor.
I use chocolate chips instead of baking bars for convenience.
Mini M&M’s or traditional rainbow sprinkles work in place of cosmic sprinkle chips.
I add a tablespoon of corn syrup for extra chewiness, like some fudgy cookie versions.
I try flavored extracts like mint or orange instead of vanilla for a festive twist.

Storage/reheating

I store cooled cookies in an airtight container at room temperature for up to 3 days. If I want the ganache firmer, I refrigerate them up to 5 days (they may firm up slightly—I bring them to room temperature before eating).
To warm them up, I microwave a cookie for about 5 seconds for a gooey, just-out-of-oven feel.

FAQs

How can I prevent the cookies from spreading too much?

I scoop the dough, chill the balls for at least 30 minutes, and bake immediately—they hold their shape much better that way.

Can I skip chilling the dough?

Chilling really helps maintain that thick, fudgy texture. If skipped, the cookies tend to flatten and lose their brownie-like chew.

My ganache is too runny—what went wrong?

If it’s too warm, I let the ganache cool longer until it can be spread without dripping—usually 15–30 minutes does the trick.

Can I freeze these cookies?

Absolutely. I freeze the cooled, un-ganached cookies for up to 3 months. I thaw, then make and spread ganache before serving.

Can I make these gluten-free?

Yes! I substitute a 1:1 gluten-free flour blend in equal measure. I haven’t tested it, but I expect them to stay fudgy and delicious.

Conclusion

I adore these Cosmic Brownie Cookies—they deliver everything I want from a deluxe chocolate cookie: rich flavor, fudgy texture, festive flair, and a creamy ganache crown. Whether I'm baking for fun, dessert, or a party, I guarantee these will vanish fast. Happy baking!

Cosmic Brownie Cookies

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Author: Sue
Prep Time: 10 minutes
Cook Time: 10 minutes
Total Time: 50 minutes (including chilling and ganache set-up)
Yield: 20 cookies
Category: Dessert
Method: Baking
Cuisine: American
Diet: Vegetarian

Print Recipe

Description

Rich and fudgy chocolate cookies inspired by nostalgic cosmic brownies, topped with silky ganache and colorful sprinkles for a decadent treat.

Instructions

In a stand mixer, whisk together melted butter, sugars, and vanilla for 1 minute.
Add eggs and mix until just incorporated.
Add flour, corn starch, cocoa powder, baking soda, and salt. Mix on low until combined.
Scoop 2–2.5 Tbsp dough balls onto parchment-lined baking sheets. Chill for 30 minutes.
Preheat oven to 350 °F. Arrange dough 2″ apart and bake for 9–10 minutes. Cool on sheet for 3 minutes, then transfer to wire rack.
Heat cream until simmering, pour over chopped chocolate, let sit for 5 minutes. Add vanilla and whisk until smooth. Let cool 15–30 minutes until spreadable.
Spread 2–3 Tbsp ganache on each cooled cookie, leaving a small border. Top with sprinkles.
Serve immediately or chill to set ganache.

Notes

Chilling the dough helps prevent spreading and keeps cookies fudgy.
Ganache should be cooled before spreading to avoid runniness.
Use dark cocoa for intense flavor or regular for a milder taste.
Store in airtight container up to 3 days at room temperature or 5 days in the fridge.
Microwave for 5 seconds to rewarm cookies.