Copycat Cosmic Brownies

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Cosmic Brownies are a childhood favorite of mine. Thick, fudgy brownies with a layer of chocolate ganache on top and sprinkled with rainbow jimmies are the ultimate in brownie creation.

Cosmic brownies stacked in front of a cast iron skillet

Homemade Cosmic Brownies

You all know by now that I’m a bit hesitant at the grocery store. I’m there nearly every other day in part because of work (photographing food for other bloggers), but I really try and buy clean, basic items when I can. However, sometimes my cravings get the best of me. Hence, the Little Debbies.

I grew up eating things like oatmeal cream pies and these cosmic brownies. And while at the store I saw an end cap with them on it. So I grabbed a box and introduced my kids to the brownies I grew up on. Low and behold, they weren’t as spectacular as I remembered. They just had a bit of an off taste to them. But I knew I could recreate this dessert at home and control the ingredients. So that’s exactly what I did.

cast iron skillet of cosmic brownies

The Secret Ingredient

Trying many different variations and recipes for these brownies led me to the secret ingredient for these thick, tender, oh-so-chocolatey brownies – cornstarch! Generally speaking I shy away from cornstarch or karo syrup. But there are some recipes where you have to have it. And to achieve the perfect Cosmic Brownie texture and thickness, this is one of them. Everything in moderation my friends! Supposedly you can replace the cornstarch with arrowroot, potato starch, and even rice flour. But I have not tried that with this recipe and most are not a 1:1 substitute. So alter with caution.

Cosmic Brownie Ingredients

  • Unsalted Butter
  • Cane Sugar
  • Brown Sugar
  • Dutch Cocoa Powder
  • Vanilla Extract
  • Eggs
  • Flour
  • Cornstarch
  • Salt
  • Semi-Sweet Chocolate Chips
  • Heavy Whipping Cream
  • Rainbow Sprinkles

Where to find rainbow sprinkles?

Cosmic brownies are known for those iconic little round rainbow sprinkles. You can’t usually find them at the grocery store, but will find them in the cake section of your local craft store like Joann’s, Hobby Lobby, etc. You don’t have to use those particular sprinkles though. It’s really just for decoration. Feel free to use whatever sprinkles you have on hand. You can also get them on Amazon if you’re not making them today.

close up of thick fudgy homemade cosmic brownies

How to make Cosmic Brownies

Preheat the oven to 350F. Spray the skillet with PAM cooking spray. Melt the butter in a microwave safe bowl. Add in the Dutch cocoa powder once melted, and whisk until smooth.

Whisk in the cane sugar and brown sugar until thick. Add the eggs and vanilla extract, and whisk until batter is smooth.

Sift the dry ingredients into the batter and fold with a rubber spatula until combined. Spread in the skillet and flatten with the rubber spatula as best as possible.

Bake for 35 minutes. Towards the end of the brownies baking, add the chocolate chips and heavy whipping cream to a microwave safe bowl. Heat for 1 minute, stirring at the 30 second mark. Whisk until smooth.

Once the brownies have baked, allow to cool slightly before topping with the chocolate ganache and sprinkles. For best results in cutting the brownies, allow to cool fully and refrigerate in the skillet for about an hour. You can certainly serve these warm but they may fall apart slightly.

Cosmic Brownie Video

How to store Cosmic Brownies

I simply left mine in the skillet cooked in and covered with plastic wrap in the refrigerator. Then I would pull it out at dinner time and by dessert they were soft enough to cut. This skillet of brownies lasted about a week. Mostly because we were eating it every day! And that was a challenge between my chocolate loving self and boys that have sweet tooths! You can certainly remove the brownies from the skillet and wrap them in plastic wrap individually to pack for lunches. Stored in a freezer they would keep for a few months and likely thawed by lunch if packed in the morning.

cast iron cosmic brownies
Cosmic Brownie Pin
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Copycat Cosmic Brownie Recipe

Course Dessert
Cuisine American
Prep Time 10 minutes
Cook Time 25 minutes
Total Time 35 minutes
Servings 8 people
Thick, dense, fudgy Copycat Cosmic Brownies are a sweet ode to the classic Little Debbie's summertime sweet. Smooth fudge-like bottom with a chocolate ganache, topped with rainbow sprinkles is bound to bring out the kid in everyone.


Brownie Base

  • 12 Tablespoons butter melted
  • 3/4 cup dutch cocoa powder
  • 1 cup sugar white or cane
  • 1/2 cup dark brown sugar
  • 2 eggs plus one yolk
  • 2 teaspoons vanilla extract
  • 3/4 cup flour all-purpose
  • 1 Tablespoon cornstarch
  • 1/2 teaspoon salt

Chocolate Ganache

  • 1 cup chocolate chips semi-sweet or milk chocolate
  • 2 Tablespoons heavy whipping cream


  • Preheat the oven to 350F. Spray the skillet with PAM cooking spray or lightly grease.
  • In a large microwave safe bowl melt the butter, approximately 2 minutes. Add the cocoa powder and whisk until smooth.
  • Add the sugars and whisk again until combined. Add the eggs plus egg yolk, and vanilla extract. Whisk until smooth.
  • In a separate bowl sift together the flour and cornstarch. Fold the flour mixture and salt to the bowl of wet ingredients using a rubber spatula.
  • Transfer to a 12-inch skillet and bake for 25 minutes or until toothpick comes out clean. Set aside to cool for 10 minutes.
  • In a microwave safe bowl add the chocolate chips and heavy whipping cream. Melt in 30 second increments and stir until smooth. Pour on top of the brownie base and decorate with rainbow sprinkles.
  • Refrigerate for 1 hour for best slicing results. Or serve immediately for a warm brownie experience.


Calories: 476kcal | Carbohydrates: 63g | Protein: 5g | Fat: 25g | Saturated Fat: 15g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 6g | Trans Fat: 1g | Cholesterol: 115mg | Sodium: 316mg | Potassium: 187mg | Fiber: 3g | Sugar: 47g | Vitamin A: 669IU | Vitamin C: 1mg | Calcium: 41mg | Iron: 2mg

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One Comment

  1. 5 stars
    These were a hit! Never thought to make cosmic brownies in the cast iron but they turned out AMAZING! My kids devoured them and I will be making another batch this evening.