These homemade cosmic brownies are absolutely delicious. A quick brownie recipe is topped with a luscious chocolate ganache and tons of rainbow chips!

Growing up in the '90s meant you remember treats like Dunkaroos, French Toast Cereal or sitting on your plastic blow-up chair, playing skip it, and best of all, all things Lisa Frank. One of my favorite things from the '90s was enjoying Little Debbie Cosmic Brownies in my school lunch if I was lucky!

There's something so irresistible about a frosted brownie, then you add rainbow chip crunch on top?! Weak at the knees baby!! Brownies topped with anything make me happy but chocolate and sprinkles really is a winner.

I wanted to create a homemade version, a copycat cosmic brownie, as much as I love the original, I love knowing exactly what I put into the food I enjoy.

Luckily these brownies are a cinch to make and bar the frosting set up time in the fridge, they are quite quick too!

Let's get to the recipe.

What are the ingredients

I based this brownie recipe off of my favorite thick and chewy brownies. I adjusted the recipe slightly and then baked them in a larger pan since to me Cosmic brownies should have equal parts frosting and brownie! For the fudgy brownies you'll need:

Water. Water helps to combine the ingredients and keep them moist.
Unsalted Butter and Vegetable Oil. Some prefer just to use all oil but I love the flavor butter adds to the brownies. If you used all butter the brownies would not be as moist and chewy.
Granulated Sugar. Granulated sugar sweetens these bars perfectly. Sugar is actually a wet ingredient and cooking it helps ensure its fully melted, which creates a great brownie with a crinkly top.
Bensdorp Dutch Cocoa Powder. Good quality cocoa powder makes all the difference. Dutch process has a deep chocolate flavor.
Light Corn Syrup. Just a wee bit of corn syrup helps create an extra chewy brownie texture.
Pure Vanilla Extract. Vanilla pairs beautifully with chocolate and gives these brownies a beautiful depth of flavor.
Eggs. Make sure your eggs are at room temperature so that they will evenly combine with the rest of the ingredients. Using an extra egg yolk will help produce a chewier brownie.
Baking Soda. Just a smidge helps give these brownies a little lift.
Salt. With all the sweetness salt helps balance everything out.
Cornstarch. Adding a tablespoon of cornstarch also known as cornflour helps create a tender, soft-baked brownie.
All-Purpose Flour. Only a small amount of flour is needed in this recipe, and it is important not to over mix. You don't want to develop the gluten.
Chocolate. Just like good quality cocoa powder is important, chocolate is too! I prefer to use Callebaut Chocolate Callets or Trader Joe's Pound Plus Chocolate Bars chopped up.
Candy-Coated Chocolate Pieces. I used these Candy Coated Rainbow Chips but Wilton makes Rainbow Chip Crunch, or even rainbow mini M&M's would work. And if all else fails rainbow sprinkles could be substituted.

For the chocolate frosting, we'll make a chocolate ganache. You'll need:

Chocolate. Since chocolate is the star here it's important to make sure you use good quality. I prefer to use Callebaut Chocolate Callets. I used a mixture of dark and milk but you could use semi-sweet chocolate chips.
Heavy Whipping Cream. Also, known as double cream. Make sure you use heavy whipping cream not whipping cream or single cream.
Butter. Adding just a little bit of butter adds a gorgeous shine to the ganache.

For another extra special bar try my Brookie Recipe.

stack of cosmic brownies with a bite taken out of the top one

How do you make Cosmic Brownies?

As with any recipe, you bake its imperative that your oven is properly heated. So preheat your oven to 350F/180C and line a 9X13 pan with foil and grease with non stick cooking spray. The foil will make them easier to remove later, making it easier to get nice clean slices.

In a large pot add the water, butter, sugar, corn syrup, and cocoa powder. Cook on medium heat for 2-3 minutes until it is all combined together. Take off of the heat and let cool for 5 minutes.

cocoa powder, butter, corn syrup, sugar and water mixed together in a metal pot

Once cooled add the oil, vanilla, egg, and egg yolk. The reason you are letting the mixture cool is so that when you add the eggs you don't accidentally scramble them!

eggs and oil added to brownie batter in a metal pot

Whisk everything together to combine, this may take a minute or two for the eggs to be fully incorporated. Make sure you scrape down the sides of the bowl so everything is cohesive.

hand holding a whisk mixing brownie batter

Stir in the baking soda, salt, cornstarch and mix to combine. Gently add the flour and chocolate chips by using a spatula to fold in until just combined. Do not over mix, this will affect the end product.

brownie batter in a metal pot with cornstarch, baking soda, flour and chocolate chips

Pour the brownie batter into prepared baking pan and bake 14-18 minutes. Don't overbake the brownies. You want a toothpick in the center to come out with moist crumbs, not completely dry. Place the pan on a wire rack to cool completely.

chocolate brownies before and after baking

Over medium-low heat cook the cream in a saucepan for a few minutes, just until warmed through, you do not want to boil the cream.

cream poured into a glass bowl of chocolate and butter

In a large heatproof bowl add the chocolate and butter then pour the warmed heavy cream on top. Let the mixture sit, unstirred, for 5 minutes.

chocolate ganache ingredients in a large glass bowl

Use a whisk to mix everything together. There should be no lumps. If there is then microwave for 15 seconds, make sure you are using a large microwave-safe bowl.

chocolate ganache in a glass measuring bowl

Pour over cooled brownies and use an offset spatula to gently create and even layer of frosting.

hand holding an angled spatula spreading chocolate frosting on top of brownies

Sprinkle on raimbow chips.

chocolate frosted brownies with rainbow chip crunch pieces on top

Place pan in the fridge for at least 1 hour to allow the frosting to set up. Slice into bars and store any leftovers in an airtight container in the refrigerator.

I hope you and your friends enjoy these copy cat Debbie cosmic brownies!

If you're looking for another copycat recipe try my cream cheese-filled pumpkin muffins or lemon pound cake.

★★★★★ Please let me know if you make this recipe by leaving a star rating and comment below!

Make sure to join our Newsletter and follow us on Pinterest, Instagram, Facebook, & Twitter.

Recipe Card

Cosmic Brownies

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

No reviews

Print Recipe

These homemade cosmic brownies are absolutely delicious. A quick brownie recipe is topped with a luscious chocolate ganache and tons of rainbow chips! Step-by-step photos help you make this easy dessert recipe.

Total Time: 2 Hours 25 Minutes
Yield: 16 Bars 1x

Instructions

Preheat your oven to 350F/180C and line a 9X13 pan with foil and grease heavily.
In a large pot add the water, butter, sugar, corn syrup, and cocoa powder. Cook on medium heat for 2-3 minutes until it is all combined together. Take off of the heat and let cool for 5 minutes.
Add the oil, vanilla, egg, and egg yolk. Whisk to combine, this may take a minute or two for the eggs to be fully incorporated.
Add the baking soda, salt, cornstarch and mix to combine. Gently add the flour and chocolate chips by using a spatula to fold in until just combined. Do not over mix, this will affect the end product.
Pour into prepared pan and bake 14-18 minutes. Don't overbake the brownies. You want a toothpick in the center to come out with moist crumbs, not completely dry. Place the pan on a wire rack to cool completely.

Frosting

Over medium-low heat cook the cream in a saucepan for a few minutes, just until warmed through, you do not want to boil the cream.
In a large heat proof bowl add the chocolate and butter then pour the warmed cream on top. Let the mixture sit, unstirred, for 5 minutes. Use a whisk to mix everything together. There should be no lumps. If there is then microwave for 15 seconds, make sure you are using a large microwave-safe bowl.
Pour over cooled brownies and use an offset spatula to gently create and even layer of frosting. Sprinkle on raimbow chips. Place pan in the fridge for at least 1 hour to allow the frosting to set up. Slice into bars and store any leftovers in an air-tight container in the refigerator.