These Homemade Cosmic Brownies Take Me Straight Back to the Lunchroom
If you grew up on those shiny-packaged Cosmic Brownies from the snack aisle, you already know how iconic they are. Dense, fudgy, coated in rich chocolate frosting, and topped with those colorful candy-coated chips—pure childhood magic. I used to trade snacks at lunch just to get my hands on one. Now? I make them at home, and honestly, they’re even better.
These brownies are soft, chewy, and covered in a glossy ganache that sets into a rich layer of chocolatey perfection. And don’t worry, those rainbow candy pieces are still front and center. They’re fun to make, even more fun to eat, and one of those nostalgic treats that hits all the right notes as an adult.
Why These Cosmic Brownies Work So Well
I’ve tried a lot of brownie recipes, but this one is a favorite for good reason:
- Fudgy and chewy texture: Just like the original—no cakey brownies here.
- Silky chocolate ganache: It sets beautifully without being too hard or too soft.
- Topped with rainbow chips: A must-have for that signature look and crunch.
- Easy to make at home: No weird ingredients or special tools needed.
- Freezer-friendly: These store and reheat beautifully for later snack attacks.
Ingredients You’ll Need
(Makes 9–12 brownies | Prep Time: 15 minutes | Bake Time: 20–25 minutes | Chill Time: 1 hour)
For the brownies:
- 1/2 cup unsalted butter, melted
- 3/4 cup granulated sugar
- 1/4 cup brown sugar
- 2 large eggs
- 1 teaspoon vanilla extract
- 1/3 cup unsweetened cocoa powder
- 1/2 cup all-purpose flour
- 1/4 teaspoon salt
- 1 tablespoon cornstarch (for extra chewiness)
For the ganache topping:
- 1/2 cup heavy cream
- 1 cup semi-sweet chocolate chips
For the topping:
- Rainbow candy-coated chocolate chips (you can find “rainbow chip sprinkles” online or in baking aisles)
How I Make Homemade Cosmic Brownies
1. Preheat and Prep
I preheat the oven to 350°F and line an 8×8-inch baking dish with parchment paper, leaving a bit of overhang on the sides for easy removal.
2. Mix the Brownie Batter
In a large bowl, I whisk together the melted butter, granulated sugar, and brown sugar until combined. Then I add the eggs and vanilla, whisking until the mixture is smooth and glossy.
In a separate bowl, I combine the flour, cocoa powder, cornstarch, and salt. I gradually fold the dry ingredients into the wet mix until just combined—careful not to overmix. The batter should be thick.
3. Bake the Brownies
I pour the batter into the prepared pan, smoothing it out evenly. Then I bake for 20–25 minutes, or until a toothpick comes out with a few moist crumbs. I let the brownies cool completely before adding the ganache.
4. Make the Ganache
In a small saucepan, I heat the heavy cream until it’s just about to simmer—then I pour it over the chocolate chips in a heat-safe bowl. I let it sit for a minute or two, then stir until smooth and glossy.
5. Frost and Decorate
Once the brownies are cooled, I pour the ganache over the top and spread it evenly with a spatula. While it’s still warm, I sprinkle on the rainbow chips so they stick perfectly.
6. Chill and Slice
I refrigerate the brownies for about an hour to let the ganache set. Once firm, I lift them out using the parchment overhang and cut them into perfect squares.
My Tips for the Best Cosmic Brownies
- Don’t overbake: Keep them fudgy by pulling them out when there are still a few moist crumbs on the toothpick.
- Cornstarch = chewy magic: It gives that classic soft-bite texture.
- Chill before slicing: You’ll get clean, sharp edges without dragging the ganache.
- Use good cocoa powder: It makes all the difference in rich, chocolate flavor.
- Double the ganache: If you’re a chocolate lover, go big on the topping layer.
When I Make These (And Why They’re Always a Hit)
These brownies show up any time I want to bring the fun:
- Birthday parties—especially for kids, but adults love them too
- Lunchbox treats—wrap individually for an old-school surprise
- Potlucks or bake sales—they always get snatched up first
- Sleepovers or movie nights—nostalgia in every bite
- Just because I need chocolate—and let’s be honest, that’s often
They’re also great for gifting—wrap a few in a cute box and you’ve got a throwback-style sweet that looks like it came from a bakery.
FAQs From My Kitchen
Q: Can I freeze these brownies?
Yes! Freeze cut squares in an airtight container with parchment between layers. Thaw in the fridge or at room temp when ready to eat.
Q: Where do I find the rainbow chips?
They’re often sold as “rainbow chip sprinkles” or “confetti baking chips.” Look online or in the baking aisle near chocolate chips.
Q: Can I use a boxed brownie mix?
You can, but the texture won’t be quite the same. If you go that route, make sure it’s a fudgy mix—not cakey.
Q: How long do they last?
Stored in the fridge, they stay fresh for up to 5 days. Let them come to room temp before serving for best texture.
Q: Can I make them in a larger pan?
Yes, but double the recipe for a 9×13 pan and adjust the baking time accordingly.
Why These Cosmic Brownies Are a Forever Favorite
They’re fudgy, nostalgic, and way more delicious than the store-bought kind I grew up on. The homemade ganache and chewy brownie base give them that bakery-style quality, and the rainbow topping adds a playful touch that makes people smile before they even take a bite. Whether you’re baking with kids, recreating a favorite snack, or just need a chocolate fix, these Cosmic Brownies are a guaranteed win.
The Copycat Cosmic Brownies Recipe That’s Pure Nostalgia with Every Bite
Ingredients
- 2 cups unsalted butter
- 4 cups granulated sugar
- 4 cups brown sugar
- 1 teaspoon vanilla extract
- 3 cups unsweetened cocoa powder
- 2 cups all-purpose flour
- 4 teaspoons salt
- 1 tablespoon cornstarch (for extra chewiness)
- 2 cups heavy cream
- 1 cup semi-sweet chocolate chips
- 1 cup chocolate frosting (for topping)
- Rainbow sprinkles (for garnish)
Instructions
- Preheat your oven to 350°F (175°C) and grease a large baking pan.
- In a large mixing bowl, cream together the unsalted butter, granulated sugar, and brown sugar until smooth and fluffy.
- Add the vanilla extract and mix until combined.
- Sift in the cocoa powder, flour, salt, and cornstarch, and mix until just combined.
- Fold in the heavy cream and semi-sweet chocolate chips until the batter is smooth.
- Pour the brownie batter into the prepared baking pan and spread evenly.
- Bake for 30 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.
- Let the brownies cool completely in the pan before frosting.
- Spread a layer of chocolate frosting over the cooled brownies and sprinkle with rainbow sprinkles.
- Cut into squares and serve.
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