Back to school has me feeling all the feels for old-school treats, these homemade Cosmic Brownies being one of them. Let me be very clear, these copycat cosmic brownies are rich, ultra fudgy, and moist.

We take that perfectly dense brownie base and top it with a decadent and silky chocolate ganache. These beautiful chocolate treats put Little Debbies Cosmic Brownies to shame.

A Cosmic Brownie with a bite taken out of it.

I’m a huge brownie fan. From the batter to the baked brownie bars, I am a brownie girl. You’ve probably figured that out already with how many brownie recipes I’ve posted for you guys. The nutella brownies have been a huge hit, so I’ve wanted to post more delicious brownie recipes from my arsenal that I know you guys will love just as much. If you haven’t checked out my German chocolate brownie bars, you definitely should! It has that delicious, gooey coconut topping on it that I literally eat plain, by the spoonful!

Whether it’s fudgy brownies or brownie cookies, my favorite thing about brownies is the rich chocolate flavor and the creamy thick texture. And this cosmic brownies recipe delivers on both of those fronts. 

The brownie batter has a bit of cornstarch in it which gives us that thick, dense chocolate bar we love. Topped with a rich, creamy ganache, you just really can’t go wrong!

And before we continue, I have to point out the photo below because it illustrates just how dense and fudgy the brownie base truly is.

And the ganache!! It’s perfect. If you’ve struggled with ganache in the past, but don’t fret because I’m sharing some great tips and tricks to get that perfect, silky smooth chocolate ganache.

Cosmic brownies on a white parchment paper.

Ingredients for Cosmic Brownies

  • Granulated sugar
  • Light brown sugar – adds moisture and sweetness. 
  • Unsalted butter – melted
  • Eggs – provides structure to the brownies as well as moisture and protein.
  • Egg yolk – adds moisture to the brownies.
  • Vanilla extract – adds flavor.
  • All purpose flour – adds structure to the brownies.
  • Unsweetened natural cocoa powder
  • Cornstarch — Like I said above, adding the cornstarch to the brownie batter helps thicken the mixture and creates that dense and creamy brownie base.
  • Salt
  • Rainbow chips – you can buy these at Michaels, Joann’s, or Amazon

How to Make Cosmic Brownies

  1. Before you begin mixing the ingredients, preheat your oven to 350°F. Line a 13×9 inch pan with foil and lightly spray it with cooking spray OR use parchment paper. If you use parchment paper you don’t have to spritz it with cooking spray, but it doesn’t hurt to do so.
  2. In the bowl of a stand mixer, or with hand beaters, beat the melted butter, brown sugar, and sugar on medium speed for 3 minutes.
    Melted butter and brown sugar in a glass bowl, for making Cosmic Brownies.
  3. Add the eggs and egg yolk, one at a time, beating well after each addition.
  4. Add the vanilla and mix that in really nicely.
  5. In a small bowl whisk the flour, cocoa powder, cornstarch, and salt.
  6. Add the dry ingredients to the wet ingredients and mix until just combined. The batter is quite thick! So don’t worry if it seems too thick. That’s how we want it.
    Thick cosmic brownie batter in a glass bowl.
  7. Spoon the batter into the prepared pan. Using a spatula level the batter so that it’s in an even layer.
  8. Bake for 20-25 minutes.

Pro tip: Don’t over bake. The biggest culprit to dry brownies is over baking them! All ovens vary. I have an oven thermometer in my oven at all times; but just remember to check the brownies periodically. 

Remove from the oven and let brownies cool in the pan. Note: they don’t need to be fully cooled before spreading the ganache overtop, but the brownies should be on the cooler side.

Ingredients for Homemade Ganache

  • Semi-sweet chocolate — you can use 1 1/4 cups of chocolate chips OR finely chopped chocolate. I used chocolate chips because I always have them in my pantry.
  • Heavy cream
  • Pinch of salt — This is not absolutely necessary. It’s just a bit of contrast to the chocolate, so omit it if you must. No one will be able to tell.

Chocolate chips and heavy cream in a bowl for making ganache.

How to Make Smooth Chocolate Ganache

  1. Place the chopped chocolate, or chocolate chips, in a medium-sized, heat-proof bowl.
  2. In a small saucepan over medium heat, warm the heavy cream. Bring to a simmer; once it’s almost boiling, remove from heat and pour the heavy cream over the chocolate. Add a pinch of salt.
  3. Let the heavy cream sit over the chocolate for 3 minutes before stirring.
  4. After 3 minutes, use a small whisk and slowly begin whisking the cream and chocolate, starting in the center of the bowl and slowly moving towards the edges.
  5. The ganache will get smooth. Once smooth, let the ganache sit for 4-5 minutes and then pour it over the brownies and spread it into an even layer with a spatula.

Ganache Bonus tip: I’ve seen others use a variation of chocolate with their ganache; some do half milk chocolate and half semi-sweet. You can definitely do this. But I have to make a disclaimer and say I’ve never done this before so I’m not sure if it turns out as great.

Once you have the ganache in an even layer over the brownies, sprinkle with rainbow chips.

Allow the ganache on the brownies to set, about 2-3 hours before cutting and serving. You can also place the brownies in the fridge instead for 30-45 minutes to speed up the setting process.

A whisk in a bowl full of chocolate ganache.

Recipe Tips

  • For the ganache: Like noted above, let the hot cream sit over the chocolate for at least 3 minutes. This waiting period lets the cream melt the chocolate while bringing down the temperature of the cream. If you whisk the cream and chocolate while the cream is still really hot (and fresh from the saucepan) it can cause the ganache to break which will result in a gritty texture.
  • Be sure to whisk the dry ingredients together in a separate bowl. Since you have the cornstarch in there, you really want to make sure all the dry ingredients are incorporated evenly. This will help when mixing the dry ingredients into the wet ingredients for a more even dispersion of the cornstarch — resulting in a thick consistency across the entire pan. 
  • I wouldn’t start making your ganache until a few minutes before your brownies are ready for the ganache. You don’t want your ganache to harden in the bowl while your brownies are still baking or are just out of the oven.

Cosmic Brownies cut into squares.

FAQs

  • When were cosmic brownies invented? — I’m not sure the exact date for when the cosmic brownies came out, but the company behind them, Little Debbie, started in 1960. 
  • What makes cosmic brownies so thick? — I’m not sure about the store-bought recipe, but in my recipe we use cornstarch to get that thick texture.
  • Can you freeze brownies? — Yes! If you are interested in freezing these brownies, here are a few tips. First, I recommend freezing the brownies without the ganache. Dairy-based foods don’t freeze well. When thawed, dairy products can separate, and that would affect the taste, texture and look of the ganache on the brownies. To freeze brownies, cut the brownies into squares and then wrap them in plastic wrap, two times, and then store in a zip top bag. They should keep in the freezer up to one month. When you are ready to eat them, pull them out and let them come to room temperature, make the ganache and spread on top of the individual brownie squares, then sprinkle with rainbow chips.

Now you’re squared away with all the tips and tricks you need to make these cute cosmic brownies! If you have kids, I know they’ll be tickled to find this delicious treat in their lunchbox.

A bite taken out of a cosmic brownie.

More Back to school recipes:

Cosmic brownies on a white parchment paper.
Print Review
5 from 1 vote

Cosmic Brownies

These homemade cosmic brownies are ultra rich and fudgy! Dare i say, WAY BETTER than the store bought version.
Prep Time: 15 mins
Cook Time: 25 mins
Total Time: 40 mins
Servings: 24 brownies

Ingredients
 

  • 1 cup granulated sugar
  • 3/4 cup light brown sugar - packed
  • 12 tablespoons unsalted butter - melted
  • 2 large eggs
  • 1 egg yolk
  • 1 teaspoon vanilla extract
  • 1 cup all purpose flour
  • 3/4 cup unsweetened natural cocoa powder
  • 2 teaspoon cornstarch
  • pinch salt
  • rainbow chips

Ganache

  • 8 oz semi-sweet chocolate - chopped OR 1 1/4 cups chocolate chips
  • 1/2 cup heavy cream
  • pinch salt

Instructions
 

Brownies

  • Preheat oven to 350°F. Line a 13x9 with parchment paper, or with foil (then lightly spray with cooking spray if using foil). 
  • In the bowl of a stand mixer fitted with a paddle attachment, or using hand beaters, beat the melted butter, brown sugar, and sugar on medium speed for 2 minutes.  
  • Add the eggs and egg yolk, one at a time, beating well after each addition. Add the vanilla and mix again.
  •  In a small bowl whisk the flour, cocoa, cornstarch, and salt. 
  • Add the dry ingredients to the wet ingredients and mix until just combined. 
  • Spoon the batter into the prepared pan. Using a spatula, level the batter so that its in an even layer. 
  • Bake for 18-24 minutes. (don’t overbake or they will be dry. Mine baked for about 21 minutes).
  • Remove from the oven and let brownies cool in the pan. 
  • While cooling make the ganache. 

Ganache

  • To make ganache, place the chopped chocolate or chocolate chips in a medium sized heat proof bowl. 
  • In a small saucepan over medium heat, warm the heavy cream. Bring to a simmer, once it’s almost boiling remove from heat and pour the heavy cream over the chopped chocolate. Add pinch of salt.
  •  Let the heavy cream sit over the chocolate for 3 minutes before stirring. *see notes
  • After 3 minutes, use a small whisk and slowly begin whisking the cream and chocolate, starting in the center of the bowl and slowly moving towards the edges. 
  • The ganache will get smooth. Once smooth, let the ganache sit for 5 minutes and then pour over the partially cooled brownies and spread using a spatula. 
  • Sprinkle with rainbow chips.
  • Allow ganache to set, about 2-3 hours, or you can place in fridge for 45 minutes to speed up the process. 

Notes

Ganache Making Tips: Make sure you wait 3-5 minutes after pouring the hot cream over the chocolate. The waiting period lets the cream melt the chocolate while bringing down the temp of the cream. If you whisk the cream and chocolate while the cream is still really hot it can cause the ganache to break which will result in a gritty texture.

Nutrition

Calories: 215kcal (11%)Carbohydrates: 26g (9%)Protein: 2g (4%)Fat: 12g (18%)Saturated Fat: 7g (35%)Cholesterol: 46mg (15%)Sodium: 13mg (1%)Potassium: 120mg (3%)Fiber: 2g (8%)Sugar: 19g (21%)Vitamin A: 286IU (6%)Calcium: 24mg (2%)Iron: 1mg (6%)
Course: Dessert
Cuisine: American
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