Cosmic Brownies
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I loved Little Debbie’s Cosmic Brownies as a kid, but my homemade version takes them to the next level. They’re rich and fudgy with a chewy center that melts in your mouth. The glossy ganache on top stays smooth, and rainbow chip sprinkles add that fun, nostalgic look. They’re the kind of brownie you can’t stop thinking about.
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I make them for birthday parties, lunchbox treats, and after-school snacks because they’re fun and colorful, and kids and adults both love them. They’re also perfect for potlucks since they travel well. These brownies stay fresh at room temp for 2 to 3 days, in the fridge for a week, or in the freezer for 2 to 3 months.
Ingredients You’ll Need
You’ll need all the ingredients shown in the photograph below.
How to Make Cosmic Brownies with Step-By-Step Instructions
Scroll down for the full recipe card containing a full printable recipe and measurements in both US customary and metric units.
I’ve got good news: this homemade version of our childhood favorite is surprisingly easy to make from scratch with simple ingredients, making it perfect even for beginner bakers.
Get the Oven and Pan Ready
Preheat your oven to 350°F and line a 9×13-inch baking pan with parchment paper or foil, leaving an overhang on the sides so you can lift the brownies out easily later. A nonstick baking pan works great for even baking and easy cleanup.
If you’re using foil, give it a quick spray with nonstick cooking spray to prevent sticking.
Mix the Wet Ingredients
In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth. Add the eggs, egg yolk, and vanilla, whisking until everything is fully combined and glossy.
I use a balloon whisk for this step because it incorporates air and creates a smooth, lump-free mixture.
Add the Dry Ingredients
Sift the cocoa powder, flour, and salt directly into the wet ingredients. This prevents lumps and helps distribute the cocoa evenly throughout the batter.
Mix until just combined without overworking it, then spread the brownie batter evenly in your prepared pan using an offset spatula to get it into all the corners.
SERIOUSLY GOOD
DESSERTS!
Dessert First is a collection of 61 RECIPES to show you that you can make beautiful, impressive desserts right in your own kitchen, no matter your skill level.
Immediate eBook download. No physical book available.
∙ Lemon Pound Cake
∙ Starbucks Cake Pops
∙ Boston Cream Pie
∙ Chocolate Mousse
∙ Matcha Tiramisu
...and much more!
Includes ad-free recipes like:
Bake the Brownies
Bake for 27 to 33 minutes, checking around the 27-minute mark, especially if your oven runs hot. You want a toothpick inserted in the center to come out with a few moist crumbs, not wet batter.
Let the brownies cool completely in the pan before adding the ganache; otherwise, the topping will melt and slide off.
Make the Ganache
Place your finely chopped semisweet chocolate and heavy cream in a heat-safe glass mixing bowl. Microwave in 1-minute increments, stirring after each interval, until the chocolate is fully melted and the ganache is smooth and glossy.
You can also do this on the stovetop using a small saucepan if you prefer.
Top and Chill
Spread the ganache in an even layer over the cooled brownies using an offset spatula or the back of a spoon, working quickly before it starts to set.
Sprinkle on rainbow candy-coated chocolate chips, mini M&M’s, or rainbow sprinkles immediately on top while the ganache is still wet, so they stick well and you get that signature look of these nostalgic, chewy brownies. The ganache sets pretty quickly!
After adding the colorful toppings, refrigerate for 1 to 2 hours until the ganache is nicely firm and set.
Slice and Serve
Once chilled, use the parchment overhang to lift the brownies out, then slice them into squares with a sharp chef’s knife. For clean slices, run the knife under hot water and wipe it dry before and after each cut.
Finally, serve and enjoy!
Cosmic Brownies travel beautifully because the ganache sets firm and the brownies hold their shape without crumbling. Pack them in hard-sided containers in a single layer or with parchment paper between layers if you’re stacking them to prevent sticking.
They can sit at room temperature for several hours during transport without the ganache melting, making them ideal for potlucks, bake sales, and lunchbox treats. If you’re traveling in warm weather or for longer periods, a thermal bag or a cooler’s your best bet.
Equipment
- Nonstick baking pan 9×13-inch
Ingredients
For the Brownies:
- 1 cup unsalted butter melted and slightly cooled
- 1 ¾ cups granulated sugar
- ½ cup brown sugar
- 3 large eggs at room temperature
- 1 large egg yolk at room temperature
- 1 teaspoon pure vanilla extract
- 1 cup unsweetened cocoa powder
- 1 cup all-purpose flour
- ½ teaspoon salt
For the Ganache:
- 8 ounces semisweet chocolate finely chopped
- ½ cup heavy cream
For the Topping:
- Rainbow candy-coated chocolate chips mini M&M’s, or sprinkles
Video
Instructions
- Preheat the oven to 350°F (180°C). Line a 9×13-inch baking pan with parchment or foil, leaving an overhang for easy lifting. If using foil, spray with nonstick cooking spray.
- In a large bowl, whisk together the melted butter, granulated sugar, and brown sugar.1 cup unsalted butter, 1 ¾ cups granulated sugar, ½ cup brown sugar
- Add the eggs, egg yolk, and vanilla, whisking until smooth.3 large eggs, 1 large egg yolk, 1 teaspoon pure vanilla extract
- Sift in the cocoa powder, flour, and salt. Mix until just combined. Spread the batter evenly in the prepared pan.1 cup unsweetened cocoa powder, 1 cup all-purpose flour, ½ teaspoon salt
- Bake for 27–33 minutes, or until a toothpick comes out with a few moist crumbs. Let cool completely before topping with ganache.
- Place the chopped chocolate and heavy cream in a heat-safe bowl. Microwave in 1-minute increments, stirring each time, until fully melted and smooth.8 ounces semisweet chocolate, ½ cup heavy cream
- Spread the ganache evenly over the cooled brownies. Add rainbow sprinkles, mini M&M’s, or candy-coated chocolate chips.Rainbow candy-coated chocolate chips
- Refrigerate for 1–2 hours to let the ganache set before slicing.
Notes
Nutrition
SERIOUSLY GOOD
DESSERTS!
Dessert First is a collection of 61 RECIPES to show you that you can make beautiful, impressive desserts right in your own kitchen, no matter your skill level.
Immediate eBook download. No physical book available.
∙ Lemon Pound Cake
∙ Starbucks Cake Pops
∙ Boston Cream Pie
∙ Chocolate Mousse
∙ Matcha Tiramisu
...and much more!
Includes ad-free recipes like:
How to Store Leftovers
Keep leftover brownies in an airtight container at room temperature for 2 to 3 days, or in the fridge for up to a week if you want the ganache to stay extra firm.
For longer storage, wrap each brownie in BPA-free plastic wrap, then place it in a freezer bag or container and freeze for 2 to 3 months. Thaw frozen brownies in the fridge overnight or on the counter for about an hour before serving.
What to Serve With Cosmic Brownies
The brownies are rich and chocolatey, so they pair well with a cold glass of milk, vanilla ice cream, whipped cream, or a drizzle of caramel sauce.
I also like serving them with fresh berries for a little tartness that cuts through the chocolate. They’re perfect on a dessert platter with sugar cookies, blondies, or Rice Krispies treats, adding variety to parties and potlucks.
You can also pack them in lunchboxes with string cheese and crackers for a fun treat, or serve them as an after-dinner dessert with coffee or hot chocolate.
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