Homemade Cosmic Brownies (Fudgy and Topped with Rainbow Candy Chips)

These cosmic brownies are dense, fudgy, and loaded with colorful candy-coated chips just like the kind you remember from childhood. They come together with basic pantry ingredients and taste even richer than the packaged version without any weird aftertaste.

The chocolate frosting sets up glossy and smooth, holding the rainbow candy pieces in place. You’ll only need one pan and a few minutes of hands-on time.

Why These Cosmic Brownies Hit the Spot

The brownie base is dense and fudgy without being overly sweet. A thin layer of chocolate frosting sets up with a slight shine, while the rainbow candy chips bring a satisfying crunch that takes you right back to the lunchbox treat, but made with real butter and melted chocolate so every bite tastes fuller.

I’ve tested the ratios a few times to get the texture just right, and this version disappears from the pan faster than any other brownie I bake. It’s simple enough for a weekend dessert, but the bright colors make it feel like an occasion.

Ingredients

• 1/2 cup unsalted butter, melted: a light-colored metal baking pan helps brownies bake evenly.
• 1 cup granulated sugar: regular white sugar works; no need for brown sugar here.
• 2 large eggs: room temperature eggs incorporate more smoothly.
• 1 teaspoon vanilla extract: pure vanilla gives a deeper, warmer flavor.
• 1/2 cup unsweetened cocoa powder: Dutch-processed or natural both work.
• 1/2 cup all-purpose flour: spoon and level to measure so the brownies stay fudgy.
• 1/4 teaspoon salt: just enough to balance the sweetness.
• 1/4 cup unsalted butter, softened: for the frosting.
• 1/4 cup unsweetened cocoa powder: for the chocolate frosting.
• 2 cups powdered sugar: sifted if it has lumps.
• 3 tablespoons milk: any milk you have on hand; adds creaminess.
• 1/2 teaspoon vanilla extract: rounds out the frosting flavor.
• 1/3 cup mini rainbow candy-coated chocolate chips: look for mini M&M’s or similar rainbow candies for the classic look.

Variations / Substitutions

• Dairy-free: use a plant-based butter stick and oat milk; check your chocolate chips for dairy.
• Gluten-free: swap in a 1-to-1 gluten-free flour blend; the texture will still be fudgy.
• No mini rainbow chips?: press regular M&M’s into the frosting instead; they’ll be larger but equally colorful.
• Deeper chocolate: stir 2 ounces of melted bittersweet chocolate into the brownie batter for extra richness.

Fudgy Brownie Bottom Cheesecake is next on our list if these brownies are your kind of dessert.

How to Make Cosmic Brownies

Step 1: Mix the Brownie Batter

Preheat your oven to 350°F (180°C). Grease a 9×13-inch metal baking pan with butter or line it with parchment. In a small bowl, whisk together the 1/2 cup flour, 1/2 cup cocoa powder, and 1/4 teaspoon salt. In a larger bowl, stir the 1/2 cup melted butter and 1 cup sugar with a spatula until combined, about 1 minute. Add the 2 eggs and 1 teaspoon vanilla, then whisk until smooth, about 30 seconds. Pour the dry ingredients into the wet and fold everything together just until no dry streaks remain. Do not overmix once the flour goes in.

The batter will look thick and glossy with a deep chocolate color. A few tiny lumps from the butter are fine, they’ll melt during baking.

Step 2: Bake the Brownies

Scrape the batter into the prepared pan and spread it into an even layer with the spatula. It will be a thin coat, about a quarter inch thick, which is exactly what you want for cosmic brownies. Bake on the middle rack for 20 to 22 minutes. The top will look set and the edges may begin to pull away slightly from the sides of the pan. A toothpick inserted in the center should come out with a few moist crumbs clinging to it.

At the 20-minute mark, peek through the oven window. If the center still looks wet and jiggly, give it another 2 minutes, but no more. Overbaking even a minute can turn them cakey instead of fudgy. Let the brownies cool completely in the pan on a wire rack before you frost them, about 1 hour.

Step 3: Whip the Frosting

While the brownies cool, make the frosting. In a medium bowl, beat the 1/4 cup softened butter with an electric mixer on medium speed until creamy, about 30 seconds. Add the 1/4 cup cocoa powder, 2 cups powdered sugar, 3 tablespoons milk, and 1/2 teaspoon vanilla. Beat on low until the sugar is mostly absorbed, then increase to medium and beat for about 2 minutes, scraping the bowl halfway through. The frosting should be smooth, thick, and spreadable with a glossy finish.

If it’s too stiff to spread, add milk 1 teaspoon at a time. If it’s too thin, beat in a little more powdered sugar. Taste it at this stage and adjust if you want a stronger chocolate note, but the final frosted brownies will already be deeply chocolaty.

Step 4: Frost and Top with Candy Chips

Once the brownies are completely cool, spoon the frosting onto the surface and spread it right to the edges with an offset spatula or the back of a spoon. Work quickly because the frosting will begin to set within a few minutes. Immediately scatter the 1/3 cup mini rainbow candy chips evenly over the top and press them very gently into the frosting so they stick.

The rainbow candy pieces will pop against the dark chocolate frosting, making the whole pan look like a sheet of cosmic treats. Let the frosting set at room temperature for at least 30 minutes before slicing, or pop the pan in the fridge for 20 minutes to speed things up.

Tips for the Best Cosmic Brownies

• Use a metal baking pan rather than glass or ceramic, it conducts heat better and gives the edges a pleasant, chewy texture without overbaking the center.
• Spoon your flour into the measuring cup and level it with a knife. Too much flour makes the brownies dry and crumbly, which no amount of frosting can fix.
• If the frosting thickens while you work, beat in milk a teaspoon at a time. A tiny bit of extra milk loosens it without making it runny.
• The brownie base can be baked a day ahead. Wrap it tightly and store at room temperature, then frost and top the next day.

Bake times for different pan sizes:

Storing Leftover Cosmic Brownies

• Room temperature: Keep brownies in an airtight container at room temperature for up to 3 days. The frosting will stay soft and the candy chips crunchy.
• Refrigerate: Store in the fridge for up to 5 days. Let them sit out at room temperature for 15 minutes before serving so the frosting softens again.

What To Serve With Cosmic Brownies

A glass of cold milk is the classic pairing; the creamy milk cools the rich chocolate and makes each bite feel even more indulgent. For a dessert upgrade, serve the brownies warm with a scoop of vanilla ice cream, the candy chips soften slightly and add a fun pop of color. Coffee or a strong espresso cuts through the sweetness nicely if you’re serving them to adults.

Frequently Asked Questions

Can I use a glass baking dish instead of metal?

Yes, but the brownies will bake more slowly and may come out softer in the center. Keep the same temperature and add 3 to 4 minutes, checking for moist crumbs on a toothpick.

My frosting turned out lumpy. What happened?

Lumpy frosting usually means the butter was too cold or the powdered sugar wasn’t sifted. Beat the frosting a minute longer to smooth it out, and if clumps remain, press it through a mesh strainer before spreading.

Can I make the brownie batter ahead of time?

You can mix the batter, cover the bowl, and refrigerate it for up to 24 hours ahead. Let it sit at room temperature for 20 minutes before spreading it in the pan and baking as directed.

Why did my candy chips sink into the frosting?

If the frosting is very warm or too thin, the chips can sink. Wait a few minutes after mixing the frosting so it cools slightly, then immediately sprinkle and press the chips. The frosting should be spreadable but hold its shape.

Cosmic Brownie Recipe

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 22 minutes mins

Total Time 37 minutes mins

Servings: 16 servings

Calories: 230

Ingredients Method Notes

Ingredients

  

• 1/2 cup unsalted butter, melted
• 1 cup granulated sugar
• 2 large eggs
• 1 teaspoon vanilla extract
• 1/2 cup unsweetened cocoa powder
• 1/2 cup all-purpose flour
• 1/4 teaspoon salt
• 1/4 cup unsalted butter, softened
• 1/4 cup unsweetened cocoa powder
• 2 cups powdered sugar
• 3 tablespoons milk
• 1/2 teaspoon vanilla extract
• 1/3 cup mini rainbow candy-coated chocolate chips

Method

 

1. Preheat oven to 350°F (180°C) and grease a 9×13-inch metal baking pan. Whisk flour, cocoa, and salt in a small bowl.
2. In a large bowl, stir melted butter and sugar until combined, about 1 minute. Add eggs and vanilla, whisk until smooth, about 30 seconds. Fold in dry ingredients just until no streaks remain. Spread batter into the prepared pan.
3. Bake 20 to 22 minutes, until a toothpick comes out with moist crumbs. Cool completely in the pan on a wire rack.
4. Beat softened butter, cocoa, powdered sugar, milk, and vanilla with an electric mixer until smooth and thick, about 2 minutes. Spread frosting over cooled brownies, scatter rainbow candy chips on top, and press gently to adhere. Let set at room temperature for 30 minutes before slicing.

Notes

For clean slices, chill the frosted brownies for 20 minutes before cutting. The frosting will set up to a nice gloss at room temperature in about an hour.