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A close-up of Cosmic Brownies topped with colorful candy sprinkles, arranged on a light blue surface.

Cosmic Brownies

Author: Mandy Applegate
I make these Cosmic Brownies whenever I'm craving that nostalgic Little Debbie treat but want something richer and fudgier. The chocolate center is dense and chewy, and the glossy ganache with rainbow chip sprinkles on top makes them look fun and colorful. They're more budget-friendly too, costing less than buying multiple boxes from the store. I make them for birthday parties, lunchbox treats, after-school snacks, and potlucks because kids and adults both love them and they travel well. They 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.
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Prep Time: 20 minutes
Cook Time: 35 minutes
Chill Time: 2 hours
Total Time: 2 hours 55 minutes
Course: Dessert
Cuisine: American
Keyword: Cosmic Brownies
Servings: 24
Calories: 251kcal

Equipment

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
US Customary - Metric

Video

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Instructions

  • Preheat the oven to 350°F (180°C). Line a 9x13-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

I've included a few helpful tips below to help you achieve the best flavor and texture in these brownies.
Use parchment overhang: Line the pan with extra parchment on the sides so you can lift the whole batch out and slice cleanly without scraping up the ganache.
Don't overbake: Pull the brownies out when a toothpick comes out with a few moist crumbs, not completely clean, so they stay fudgy instead of cakey.
Let them cool completely: The chocolate ganache will slide off or melt into the brownies if you spread it on while they're still warm, so be patient and let them cool to room temperature first.
Chop the chocolate finely: Smaller pieces melt faster and more evenly in the hot cream, giving you a smoother ganache without lumps. You can swap bittersweet chocolate for the semisweet if you prefer a less sweet, more intense chocolate flavor.
Flash freeze for clean cuts: Freeze the brownies for 30 minutes before slicing if you want perfectly sharp edges and no ganache smearing on the knife.
Store properly: Keep cooled brownies sealed well at room temp for 2 to 3 days, chill for up to a week, or freeze for 2 to 3 months. To keep them from sticking together, flash-freeze on a baking sheet until hard, then transfer to freezer bags or containers. Thaw before serving.

Nutrition

Calories: 251kcal | Carbohydrates: 30g | Protein: 3g | Fat: 14g | Saturated Fat: 9g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 0.3g | Cholesterol: 55mg | Sodium: 62mg | Potassium: 136mg | Fiber: 2g | Sugar: 23g | Vitamin A: 354IU | Vitamin C: 0.03mg | Calcium: 25mg | Iron: 2mg
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