If you grew up grabbing a Cosmic Brownie from your lunchbox or the gas station checkout, this homemade version is about to become your new favorite dessert. These fudgy brownies have that rich, chewy texture we all remember, but they’re made completely from scratch and topped with a thick layer of silky chocolate ganache and those iconic rainbow candy-coated chips.
They’re everything you love about the classic treat, just richer, more chocolatey, and even better homemade.
Why You’ll Love These Homemade Cosmic Brownies
These brownies are incredibly fudgy thanks to melted butter and brown sugar, creating that dense, chewy texture that’s so nostalgic. Instead of a thin frosting, they’re finished with a smooth chocolate ganache that sets into the perfect bite before being topped with colorful candy-coated chips for that unmistakable Cosmic Brownie look.
They’re easy enough for a weekend baking project but impressive enough to bring to parties, birthdays, bake sales, or holiday cookie trays.
Tips for the Best Cosmic Brownies
- Don’t overbake the brownies. They should still have a few moist crumbs attached to a toothpick when they’re removed from the oven. They’ll continue setting as they cool.
- Allow the brownies to cool completely before adding the ganache. If they’re even slightly warm, the chocolate topping can melt into the brownies instead of sitting on top.
- Let the ganache cool for several minutes before pouring it over the brownies. This helps create that thick, distinct chocolate layer.
- Add the rainbow candy-coated chips immediately after spreading the ganache so they stick before it begins to set.
- For the cleanest slices, allow the ganache to fully set before cutting and wipe your knife clean between cuts.
- Bake the brownies in a metal square pan. This one is my favorite!
Storage
Store the brownies in an airtight container at room temperature for up to 3 days. They can also be refrigerated for up to a week, though I recommend letting them sit at room temperature for about 20 minutes before serving for the softest texture.
These brownies also freeze beautifully. Freeze individual slices or the entire pan (without cutting) for up to 3 months. Thaw overnight in the refrigerator or for a couple of hours at room temperature.
Frequently Asked Questions
Can I use Dutch-process cocoa powder?
I recommend natural cocoa powder for the best flavor and texture in this recipe.
Can I make these ahead of time?
Absolutely! In fact, they’re even better the next day once the ganache has fully set.
Do I have to use the rainbow candy-coated chips?
No, but they’re what gives these brownies their signature Cosmic Brownie look. You can substitute rainbow sprinkles if needed, though the texture will be slightly different.Final Paragraph
These homemade Cosmic Brownies are everything I loved about the classic lunchbox treat, just with an extra rich and fudgy homemade twist. The dense chocolate brownies paired with that thick, silky ganache and crunchy rainbow candies make every bite so nostalgic and delicious. Whether you grew up eating Cosmic Brownies or you’re trying them for the first time, this is one of those recipes that’s guaranteed to bring out your inner kid!
Copycat Cosmic Brownies
Ingredients
For the brownies:
- 1 cup salted butter melted
- 2 tbsp vegetable oil
- 1 ¼ cups granulated sugar
- 1 cup light brown sugar packed
- 4 eggs room temperature
- 1 tsp vanilla extract
- ½ tsp kosher salt
- 1 cup all-purpose flour
- 1 cup natural cocoa powder
For the ganache:
- 8 ounces bittersweet chocolate chopped. Or you can use semi sweet if you prefer!
- ½ cup heavy cream
- ¼ cup rainbow chips
Instructions
For the brownies:
- Preheat oven to 350°F. Line an 8×8-inch or 9×9-inch metal baking pan with parchment paper and lightly grease. In a large bowl, whisk together the melted butter, vegetable oil, granulated sugar and brown sugar until smooth.
- Add the eggs one at a time, whisking well after each addition. Stir in the vanilla. Fold in the flour, cocoa powder, and salt until just combined. Do not over mix.
- Spread the batter evenly into the prepared pan.Bake for 30-35 minutes, or until a toothpick inserted near the center comes out with a few moist crumbs attached. Allow the brownies to cool completely in the pan.
For the ganache:
- Place the chopped chocolate into a heatproof bowl. Heat the heavy cream on the stove until it just begins to simmer around the edges. Pour the hot cream over the chocolate and let sit for 2-3 minutes.
- Stir gently until completely smooth and glossy. Let the ganache cool for 5-10 minutes, until slightly thickened but still pourable. Pour over the cooled brownies and spread into an even layer. Immediately top with the rainbow candy-coated chips. Allow the ganache to set at room temperature for 1-2 hours before slicing.