This copycat recipe for Cosmic Brownies is ultra-rich, fudgy, and chewy just like the kind you buy at the store but oh so much better, with no preservatives!
Preheat the oven to 350°F. Line an 8-by-8-inch metal baking pan with parchment or foil and spray with cooking spray.
In a large microwave-safe bowl, melt the butter for about 90 seconds on high power. Stir in the granulated sugar, brown sugar, and cocoa powder. If still very hot, let cool slightly before adding in the vanilla, eggs, egg yolk, and corn syrup. Stir until very well combined. Add in the flour, cornstarch, and salt and stir until just combined. Batter will be thick. Pour into the prepared pan and bake for 25 minutes. Let cool completely in the pan.
Make the frosting:
Place the cream in a small microwave-safe bowl and microwave on high for 1 minute. Add in the chocolate chips. Let stand for 3 minutes before stirring until smooth. Pour over the cooled brownies and smooth evenly. Sprinkle with the Rainbow Candy-Coated Chocolate Chips. Refrigerate for 1 to 2 hours, or until the frosting is set, before cutting.
Brownies can be stored in an airtight container for 3 days at room temperature and for 1 week in the fridge. Brownies are best served chilled.
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Notes
Where to Find Rainbow Candy-Coated Chocolate Chips?
I used to use Wilton Rainbow Crunch for topping Cosmic Brownies, but those are increasingly difficult to find. This Baker's Choice version is available on Amazon, but feel free to use rainbow sprinkles, mini M&Ms, or whatever you like to top these brownies.