Chaos Cake Sheet Pan Brownies (Print Version)

Brownie-cake bars packed with chocolate, cookies, and colorful sprinkles for festive, fun gatherings.

# What You’ll Need:

→ Brownie-Cake Base

01 - 1 cup unsalted butter, melted
02 - 1 1/2 cups granulated sugar
03 - 1/2 cup packed light brown sugar
04 - 3 large eggs
05 - 2 teaspoons vanilla extract
06 - 1 cup all-purpose flour
07 - 1/2 cup unsweetened cocoa powder
08 - 1 teaspoon baking powder
09 - 1/2 teaspoon salt

→ Add-Ins

10 - 3/4 cup semi-sweet chocolate chunks
11 - 1/2 cup rainbow sprinkles
12 - 1 cup birthday cake-flavored sandwich cookies, roughly chopped

→ Frosting and Topping

13 - 1/2 cup unsalted butter, softened
14 - 2 cups powdered sugar, sifted
15 - 2 tablespoons milk
16 - 1/2 teaspoon vanilla extract
17 - Pinch of salt
18 - Additional rainbow sprinkles for topping

# How to Make It:

01 - Preheat the oven to 350°F. Line a 9x13-inch sheet pan with parchment paper, leaving an overhang for easy removal.
02 - In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth and glossy.
03 - Add the eggs one at a time, whisking thoroughly after each addition. Stir in the vanilla extract.
04 - Sift in the all-purpose flour, cocoa powder, baking powder, and salt. Fold gently until just combined, taking care not to overmix.
05 - Fold in the semi-sweet chocolate chunks, rainbow sprinkles, and chopped birthday cake-flavored cookies until evenly distributed throughout the batter.
06 - Spread the batter evenly in the prepared sheet pan. Bake for 23 to 25 minutes, or until the center is just set and a toothpick inserted yields moist crumbs. Do not overbake.
07 - Allow brownies to cool completely in the pan placed on a wire rack.
08 - Beat the softened butter with an electric mixer until creamy. Gradually add sifted powdered sugar, milk, vanilla extract, and a pinch of salt, continuing to beat until the frosting is light and fluffy.
09 - Spread the prepared frosting evenly over the cooled brownies. Decorate generously with extra rainbow sprinkles.
10 - Cut into squares and serve.

# Additional Tips::

01 -
  • Uses simple kitchen staples with just a few fun extras
  • Ready in under an hour start to finish
  • Works as a birthday cake alternative or an everyday treat
  • Great for sharing and makes big batches with minimal fuss
02 -
  • Big crowd pleaser with bold flavor
  • Stays soft for days; perfect for making ahead
  • Fun way to use up leftover celebration cookies
03 -
  • Do not overbake; stop as soon as a tester has moist crumbs
  • Always cool completely before frosting so the topping stays thick and spreadable
  • Use an offset spatula or butter knife for those classic bakery style swirls
  • If your sprinkles bleed use classic jimmies, not nonpareils
  • This recipe is made to be played with so let kids help add the final sprinkles for priceless kitchen memories

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