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overhead shot of cosmic brownies

Cosmic Brownies

  • Author: Elizabeth Waterson I Confessions of a Baking Queen
  • Prep Time: 10
  • Cook Time: 15
  • Total Time: 2 Hours 25 Minutes
  • Yield: 16 Bars 1x
  • Category: Dessert
  • Method: Bake
  • Cuisine: American


These homemade cosmic brownies are absolutely delicious. A quick brownie recipe is topped with a luscious chocolate ganache and tons of rainbow chips! Step-by-step photos help you make this easy dessert recipe. 




  • 2oz (1/4 Cup) Water
  • 1oz (2 Tbsp) Unsalted Butter
  • 250 Grams(1 1/4 cups) Granulated Sugar
  • 90 Grams (3/4 cupsBensdorp Dutch Cocoa Powder
  • 2oz (scant 1/4 cup) Vegetable Oil
  • 1oz (2 Tablespoons) Light Corn Syrup
  • 1 Tablespoon Pure Vanilla Extract
  • 1 Large Egg Yolk and 1 Large Egg, at room temp.
  • 1/8 Teaspoon Baking Soda
  • 1/2 Teaspoon Salt
  • 1 Tablespoon Cornstarch/ Cornflour
  • 60 Grams (scant 1/2 cup) All- Purpose Flour
  • 2oz Chocolate (chips, chunks, or bars chopped)


  • 12oz (2 Cups) Chocolate, good quality I use Call
  • 6oz (3/4 Cup) Heavy Whipping Cream
  • 1 Tablespoon Butter
  • Rainbow Candy Coated Rainbow Chips


  1. Preheat your oven to 350F/180C and line a 9X13 pan with foil and grease heavily.
  2. In a large pot add the water, butter, sugar, corn syrup, and cocoa powder. Cook on medium heat for 2-3 minutes until it is all combined together. Take off of the heat and let cool for 5 minutes.  
  3. Add the oil, vanilla, egg, and egg yolk. Whisk to combine, this may take a minute or two for the eggs to be fully incorporated.
  4. Add the baking soda, salt, cornstarch and mix to combine. Gently add the flour and chocolate chips by using a spatula to fold in until just combined. Do not over mix, this will affect the end product.
  5. Pour into prepared pan and bake 14-18 minutes. Don't overbake the brownies. You want a toothpick in the center to come out with moist crumbs, not completely dry. Place the pan on a wire rack to cool completely.


  1. Over medium-low heat cook the cream in a saucepan for a few minutes, just until warmed through, you do not want to boil the cream.
  2. In a large heat proof bowl add the chocolate and butter then pour the warmed cream on top. Let the mixture sit, unstirred, for 5 minutes. Use a whisk to mix everything together. There should be no lumps. If there is then microwave for 15 seconds, make sure you are using a large microwave-safe bowl.
  3. Pour over cooled brownies and use an offset spatula to gently create and even layer of frosting. Sprinkle on raimbow chips. Place pan in the fridge for at least 1 hour to allow the frosting to set up. Slice into bars and store any leftovers in an air-tight container in the refigerator.

Keywords: how to make cosmic brownies, homemade cosmic brownies, frosted brownies

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