These rich, fudgy Cosmic Brownies are a homemade take on the nostalgic lunchbox favorite. Topped with smooth chocolate ganache and colorful candy-coated chips!
If you grew up loving Cosmic Brownies, you’re in for a treat. These homemade brownies capture all the fun and indulgence of the original but with even better flavor and texture. They’re rich and chewy, with a smooth ganache topping and those signature rainbow candy chips. Whether you’re baking for a party, packing lunches, or just feeling a bit nostalgic, these brownies are sure to hit the spot.
Why You’ll Love This Cosmic Brownies Recipe
- Nostalgic flavor with homemade quality. These brownies take all the best parts of the store-bought version, with their dense texture, rich chocolate, and rainbow topping, and make them even better from scratch.
- Fudgy and chewy, not cakey. The texture is exactly what a cosmic-style brownie should be—dense, rich, and chewy with just the right amount of softness.
- Simple, no-fuss ganache topping. A silky chocolate layer made with just two ingredients adds a bakery-worthy finish without any extra effort.
- Fun and colorful. The rainbow chips make these brownies perfect for parties, lunchboxes, or just adding a little joy to your everyday baking.
Key Ingredients
Here’s a look at the primary ingredients that make these brownies so irresistible. For ingredient quantities and complete instructions, see the recipe card below.
- Butter – Melted unsalted butter gives the brownies their rich, chewy texture and deep flavor. No need to cream. Just stir and go!
- Granulated and brown sugars – A mix of white sugar and light brown sugar adds sweetness and helps create that signature chewy bite.
- Cocoa powder – Unsweetened cocoa powder provides bold chocolate flavor. Natural cocoa works best here, but Dutch process can be used for a slightly darker taste.
- Eggs – Four eggs add structure and moisture, helping the brownies stay thick and fudgy.
- Heavy cream and chocolate – These two ingredients make a smooth, simple ganache for the topping.
- Rainbow candy-coated chocolate chips – The fun finishing touch! These candy-coated chips give the brownies their cosmic charm. Look for Wilton Rainbow Chip Crunch or something similar at grocery stores or craft stores. (The ones pictured here are from nuts.com.)
How to Make Cosmic Brownies
Prepare the pan and preheat the oven.
Line a 9×13-inch baking pan with parchment paper, leaving a bit of overhang on the sides for easy lifting. Lightly grease any exposed parts of the pan that aren’t covered by parchment to help prevent sticking. Preheat your oven to 350°F (180°C).
Mix the wet ingredients.
Whisk together the melted butter, granulated sugar, brown sugar, cocoa powder, salt, and vanilla until smooth and glossy. The mixture will be thick and dark. This step helps dissolve the cocoa and sugars.
Add the eggs.
Whisk in the eggs one at a time, making sure each is fully incorporated before adding the next. This step is key to building structure and that shiny top.
Stir in the dry ingredients.
Add the flour and cornstarch, stirring just until combined. Don’t over-mix. Be sure stop when you no longer see dry streaks.
Bake the brownies.
Spread the brownie batter evenly in the prepared pan and bake for 22 to 26 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Let the brownies cool completely before topping.
Make the ganache.
Heat the cream to a simmer, then pour it over the chocolate chips. Let sit for a minute or two, then stir until smooth and glossy. Cool slightly before using.
Top with ganache and rainbow chips.
Spread the ganache over the cooled brownies, then immediately sprinkle with rainbow chips. Chill for about 30 minutes to set the topping.
Slice and enjoy.
Once the ganache is set, lift the brownies out using the parchment and slice into squares.
Tips for Success
- Use room temperature eggs. They mix more easily into the batter and help create a smoother, more even texture.
- Don’t over-bake. These brownies are meant to be soft and fudgy, so look for moist crumbs on the toothpick, not a clean one. Over-baking will make them dry.
- Let them cool completely. It’s tempting to rush, but the ganache needs a cool surface to set properly. You can speed things up by placing the pan on a wire rack or even chilling it briefly.
- Chill before slicing. Place the finished brownies in the fridge for 30 minutes to firm up the ganache. This helps you get those nice, clean edges when slicing.
- Use a sharp knife and clean between cuts. For neat squares, wipe your knife clean with a damp cloth between each slice.
Variations
- Add a chocolate drizzle. For extra flair, drizzle a bit of melted chocolate over the rainbow chips once the ganache is set.
- Swap the rainbow chips. If you can’t find the classic candy-coated chips, try mini M&M’s, colorful sprinkles, or chopped chocolate candy bars.
- Make them double chocolate. Stir in 1/2 cup of mini chocolate chips or chunks into the batter for even more chocolatey goodness.
- Try a different topping. Skip the rainbow chips and top with chopped nuts, crushed cookies, or toffee bits for a twist.
How to Store
Room temperature: Store the brownies in an airtight container at room temperature for up to 3 days. If your kitchen is warm or humid, it’s best to refrigerate them to keep the ganache firm.
Refrigerator: For slightly longer storage, refrigerate them for up to 5 days. Let them come to room temperature before serving for the best texture.
Freezer: To freeze, place sliced brownies on a baking sheet and freeze until solid. Then wrap each brownie and transfer to an airtight container or zip-top bag. They’ll keep for up to 2 months. Thaw at room temperature or in the refrigerator overnight.
A Fun Throwback Worth Baking Again and Again
These Cosmic Brownie-style bars are pure nostalgic comfort, with the bonus of homemade flavor and texture that beats the original. Whether you’re baking for kids or just revisiting a childhood favorite, this easy recipe is sure to become a go-to treat.
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Cosmic Brownies
Ingredients
For the Brownies:
- 1 cup (226 g) unsalted butter, melted and slightly cooled
- 1 1/4 cups (250 g) granulated sugar
- 3/4 cup (150 g) firmly packed light brown sugar
- 3/4 cup (64 g) unsweetened cocoa powder
- 1/2 teaspoon salt
- 1 tablespoon vanilla extract
- 4 large eggs
- 1 cup (120 g) all-purpose flour
- 2 tablespoons cornstarch, for chewiness
For the Topping:
- 1 cup (170 g) semisweet chocolate, chopped
- 1/2 cup (120 ml) heavy cream
- rainbow candy-coated chocolate chips
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Instructions
To make the brownies:
- Preheat to 350°F (175°C). Line a 9×13-inch pan with parchment paper, leaving a bit of overhang. Lightly grease any exposed parts of the pan.
- In a large bowl, whisk together the melted butter, both sugars, cocoa powder, salt, and vanilla. Add the eggs one at a time, mixing well after each.
- Stir in the flour and cornstarch until just combined.
- Spread the batter evenly in the pan. Bake 22–26 minutes, or until a toothpick comes out with a few moist crumbs. Cool completely in the pan.
To make the topping:
- Heat the cream on the stovetop or in the microwave until just simmering, then pour over the chopped chocolate. Let sit 2 minutes, then stir until smooth. Cool slightly, then spread over the cooled brownies.
- Sprinkle the rainbow chips over the ganache while it’s still soft. Chill briefly to set the topping (30 minutes to 1 hour), then slice and serve.
Notes
- Rainbow chip topping: For the signature look, use candy-coated rainbow chips like the ones pictured here from nuts.com. Wilton also makes a version often sold as “rainbow chip crunch” in the baking aisle or online. Can’t find them? Try mini M&Ms, colorful sprinkles, or chopped chocolate candies for a similar pop of color and texture. Chopped nuts or toffee bits are a tasty option, too.
- Cocoa powder: Natural unsweetened cocoa is best here for a classic brownie flavor. Dutch-process will work, too. It just gives a slightly deeper color and milder flavor.
- Ganache topping: Use good-quality semisweet chocolate for the best texture and flavor. I recommend avoiding chocolate chips, as they often have stabilizers that make them more difficult to melt. If you’d like a thicker topping, slightly reduce the cream to 6 tablespoons.
- Don’t skip the parchment. These brownies are soft and fudgy, so lining the pan helps with easy removal and cleaner slicing.
- Storage tip: For the neatest slices, chill the brownies before cutting. They’re easiest to portion when cold but taste best at room temperature. Store at room temperature up to 3 days, in the refrigerator up to 5 days, or in the freezer up to 2 months.
