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Cosmic Brownies

Bringing back your favorite childhood treat! Cosmic brownies are a fudgy chocolate brownie with chocolate frosting and rainbow candy sprinkles on top. These Little Debbie copycats are amazing!
Course Dessert
Cuisine American
Keyword cosmic brownies
Prep Time 30 minutes
Cook Time 30 minutes
Total Time 1 hour
Servings 36 brownies
Calories 340kcal


  • 18 ounces good quality SEMI-SWEET chocolate chips (~3 completely full cups or 1 and 1/2 (12 ounce) bags) I don't recommend a different type of chocolate.
  • 9 tablespoons unsalted butter, cut into cubes
  • 1 cup + 2 tablespoons granulated white sugar
  • 1/2 tablespoon pure vanilla extract
  • 4 LARGE eggs + 1 large egg yolk
  • 6 tablespoons dutch process cocoa powder (Hershey's dark cocoa powder is dutch process)
  • 1/2 cup cornstarch
  • 3/4 teaspoon fine sea salt
  • 1 and 1/2 cups milk, semi-sweet, or dark chocolate chips (whatever you prefer, we like milk best)

For the frosting:

  • 1 and 1/2 cups good quality SEMI-SWEET chocolate chips
  • 1/2 cup heavy cream
  • Wilton rainbow chip crunch or mini M&M’s (or sprinkles or mini chocolate chips)


  • PREP: Line a light colored metal 9 x 13 pan with parchment paper leaving enough of an overhang to easily remove bars. Don't skip this step. Preheat the oven to 350 degrees F.
  • BROWNIES: In a VERY large microwave safe bowl, combine the chocolate chips and cubes of butter. Microwave in bursts of 15 seconds, stirring in between each burst, until completely melted and smooth. Be patient here and don't microwave too long at risk of burning chocolate. Remove from the microwave and immediately stir in the sugar. Add in the vanilla and one egg. Stir until completely incorporated. Add the remaining eggs and egg yolk, ONE at a time, stirring with a wooden spoon after each addition is completely integrated. It's thick but avoid hand/stand mixers as these will beat in too much air. In a separate bowl, stir together the cocoa powder, cornstarch, and salt. Add to the brownies along with the 1 and 1/2 cups chocolate chips. Stir until smooth. Transfer to prepared baking pan.
  • BAKE: Bake for 27-33 minutes watching very carefully near the end. As soon as a toothpick comes out with moist crumbs (make sure it doesn't hit a melted chocolate chip!) these brownies are done. This is almost always 29-30 minutes in my oven (calibrated). Differences will occur based on individual ovens, humidity, etc. Remove and allow brownies to fully cool at room temperature before topping.
  • FROSTING: Add chocolate chips to a large heat safe bowl. Place the cream in a small microwave-safe bowl and microwave on high for 1 minute. Pour over the chocolate chips. Cover bowl with the bottom of a cookie sheet or lid to a pan (whatever you have to keep heat in). Let stand for 4 minutes before stirring until smooth. (If chocolate won't melt completely, place in microwave for 15 seconds and then stir again). Once smooth, pour over the completely cooled brownies and smooth until even. Sprinkle bars evenly with the rainbow chips, sprinkles, or mini M&Ms.
  • SERVING: Place in the fridge, covered, for 1 to 2 hours, or until the frosting is completely set. To cut: remove brownies from pan using parchment paper overhang. Cut with a sharp knife. For clean cuts, run knife under hot water, dry, and make a cut. Repeat until all bars are cut out. Return leftovers to an airtight container in the fridge. Brownies are best served chilled.


Gluten free: brownies are naturally gluten free -- confirm with all packaging that products are processed in gluten free environment. Replace rainbow crunch sprinkles with miniature chocolate chips for gluten free.


Calories: 340kcal