Homemade Cosmic Brownies

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Last Updated on May 15, 2026 by Kiersten James

These homemade cosmic brownies are thick, fudgy, chocolatey, and taste just like the nostalgic Little Debbie brownies from childhood.

There are certain snacks almost every ‘90s kid remembers pulling out of a lunchbox, and cosmic brownies are right at the top of my list. 

Thick, fudgy chocolate brownies with that soft ganache layer and little rainbow candy chips on top somehow tasted better after sitting in a hot backpack half the day.

These homemade cosmic brownies have all of that same nostalgia, but they actually taste like real chocolate brownies instead of something wrapped in plastic from a gas station.

They’re dense, chewy, deeply chocolatey, and stay soft for days. They’re really fun to make for birthday parties, sleepovers, bake sales, movie nights, and honestly, just regular Tuesdays when the kids want “the astronaut brownies with sprinkles on top.”

The best part is that they’re VERY easy to make completely from scratch, and once you make them homemade, the super fake, heavily processed Little Debbie ones don’t compete anymore.

Why You’ll Love These Homemade Cosmic Brownies

• Thick, fudgy texture just like the cosmic brownies from the store
• Rich chocolate flavor without tasting artificial
• Easy enough for beginner bakers
• Perfect for lunchboxes and after-school snacks
• Freezer-friendly for quick desserts
• Fun nostalgic recipe both kids and adults love

Ingredient Highlights:

Unsalted Butter: Butter gives these brownies their rich flavor and dense texture. Using real butter instead of oil gives homemade brownies a deeper, more bakery-style taste.

Granulated Sugar + Brown Sugar: The mix of sugars is what creates that classic chewy cosmic brownie texture. Brown sugar adds moisture and softness while granulated sugar helps create those shiny brownie tops.

Eggs: Eggs help bind everything together and create structure. Whisking them well into the sugar mixture also helps give the brownies their glossy finish.

Vanilla Extract: Vanilla balances the chocolate flavor and gives the brownies warmth and depth. Homemade vanilla works especially well here.

Unsweetened Cocoa Powder: This is where the deep chocolate flavor comes from. Cocoa powder gives these brownies their dark, rich cosmic brownie taste without box mixes or artificial flavoring.

All-Purpose Flour: A small amount of flour keeps the brownies dense and fudgy instead of cakey.

Cornstarch: Cornstarch helps soften the crumb and gives the brownies a chewy, almost candy-bar texture you would expect from cosmic brownies.

Semi-Sweet Chocolate Chips: Chocolate chips melted into the batter add richness and help create the signature dense texture. They’re also used for the ganache topping.

Heavy Cream: Heavy cream creates a smooth homemade ganache that sets beautifully without becoming hard or dry.

Rainbow Candy-Coated Chocolate Chips: The rainbow chips are what make cosmic brownies look like cosmic brownies. They add crunch, color, and that nostalgic finish. These were hard to find, so I had to order them online. The bag is a bit large for a home baker, but it will keep for a very long time if you store it in the freezer.

Tips for the Best Results

• Do not overbake. Cosmic brownies should stay slightly soft in the center.
• Let the brownies cool completely before adding the ganache, or the topping will melt.
• Chill in the refrigerator before slicing for clean bakery-style squares.
• A plastic knife slices chilled brownies especially cleanly. Otherwise, you can heat a metal knife under hot water, then dry it before slicing.
• Use parchment paper or a foil sling for easy removal from the pan.
• Store brownies at room temperature for a softer texture or refrigerate for firmer brownies.

How to Make Homemade Cosmic Brownies

Ingredients:

For the Brownies:

• 1 cup unsalted butter, melted
• 1 1/2 cups granulated sugar
• 1 cup packed brown sugar
• 4 large eggs
• 2 teaspoons vanilla extract
• 1 cup unsweetened cocoa powder
• 1 cup all-purpose flour
• 1/2 teaspoon salt
• 1 tablespoon cornstarch
• 1 cup semi-sweet chocolate chips

For the Chocolate Ganache:

• 1 cup semi-sweet chocolate chips
• 3/4 cup heavy cream

Topping:

• Rainbow candy-coated chocolate chips

Instructions:

Preheat your oven to 350°F. Grease a 9×13 baking pan and line it with parchment paper or make a foil sling. Grease the paper or foil.

In a large bowl, whisk together the flour, cocoa powder, salt, and cornstarch.

In another bowl, whisk together the melted butter, granulated sugar, and brown sugar until fully combined.

Add the eggs and vanilla extract. Whisk until the mixture becomes smooth and glossy.

Pour the wet ingredients into the flour mixture, then gently mix with a wooden spoon or a stiff rubber spatula until well combined. Make sure to scrape up any trapped flour on the bottom of the bowl, but be careful not to overmix.

Fold in the chocolate chips, then spread the batter evenly into the prepared baking pan.

Bake for about 28 minutes, or until the center is just set. Rotate the pan halfway through baking to make sure it cooks evenly. It should still look slightly soft in the middle.

Allow the brownies to cool completely before adding the ganache.

To Make the Chocolate Ganache:

Heat the heavy cream in a small pot until steaming but not boiling. Add the chocolate chips and stir vigorously until melted, smooth, and glossy.

Spread the ganache evenly over the cooled brownies. Use all of the ganache for a nice, thick frosting layer.

Sprinkle the rainbow candy-coated chocolate chips over the top while the ganache is still wet.

Chill the brownies in the refrigerator until the ganache is set before slicing.

Storage & Freezing:

Store brownies in an airtight container at room temperature for up to 5 days.

To freeze, chill brownies in the refrigerator until firm. Wrap individual brownies tightly in plastic wrap and place them in a freezer-safe bag for up to 2 months.

More Fun Recipes to Bake With Kids:

Soft Chocolate Chip M&M Cookies

Chocolate Chip Cookie Bars (9×13)

Chewy Oatmeal Chocolate Chip Cookies

Big Bakery-Style Chocolate Chip Muffins

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