Crumbl Cosmic Brownie Cookies

These are thick, fudgey chocolate cookies topped with a ganache glaze and rainbow chips. They’re big enough to share but good enough that you won’t want to.

June Arthurs
March 13, 2026
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Ingredients (~18 cookies)

Cookies

  • 1 cup salted butter, softened
  • 1 cup brown sugar
  • 1/3 cup granulated sugar
  • 2 eggs
  • 1 1/2 Tbsp corn syrup
  • 2 tsp vanilla extract
  • 2 1/2 cups all-purpose flour
  • 2/3 cup dutch processed cocoa powder
  • 2 tsp corn starch
  • 1 1/2 tsp baking soda
  • 3/4 tsp salt

Toppings

  • 1/2 cup heavy cream
  • 1 1/3 cups semi sweet chocolate chips
  • 1/4 cup rainbow coated chocolate chips

Cream the Butter and Sugars

Preheat your oven to 350F.

Using a stand mixer, cream together 1 cup of softened salted butter, 1 cup of brown sugar, and 1/3 cup of granulated sugar until light in color and fluffy in texture.

This usually takes ~3-4 minutes on medium speed.

Add the Wet Ingredients

Add in 2 eggs, 1 1/2 Tbsp of corn syrup and 2 tsp of vanilla extract. Mix until thoroughly combined.

Mix in the Dry Ingredients

Add 2 1/2 cups of all-purpose flour, 2/3 cup of dutch processed cocoa powder, 2 tsp of corn starch, 1 1/2 tsp of baking soda and 3/4 tsp of salt.

Mix until your chocolate cookie dough forms. The dough will be soft and slightly sticky.

Shape and Bake the Cookies

Divide the dough into 9 equal portions – I use a 1/3 cup measuring cup which gives you the right size.

Roll each portion into a ball then flatten slightly so it looks like a hockey puck before arranging on a parchment paper covered pan. Place 6 cookies per tray; they spread a bit.

Bake at 350F for ~15-17 minutes. The cookies should start to crack and crinkle, spread slightly, and the centers should no longer look wet.

Make the Fudge Frosting While the Cookies Bake

Measure out 1/2 cup of heavy cream into a microwave safe bowl.

Microwave the cream for ~1 1/2 minutes or until it’s boiling.

Remove from the microwave and add 1 1/3 cups of semi sweet chocolate chips. Use a spoon to push the chocolate chips around so they’re all covered by the hot cream.

Allow the chocolate chips to sit in the hot cream for 3 minutes.

After 3 minutes, whisk the chocolate chips into the heavy cream until smooth. Set aside and let it cool while the cookies finish baking.

Top the Cookies

Once the cookies are out of the oven, let them cool on the pan for ~10 minutes.

Spoon the frosting onto the top of each cookie and sprinkle with 1/4 cup of rainbow coated chocolate chips while the icing is still wet.

The frosting will set up as it cools but these are best served while still warm.

Crumbl Cosmic Brownie Cookies

These are thick, fudgey chocolate cookies topped with a ganache glaze and rainbow chips. They’re big enough to share but good enough that you won’t want to.
prep time15 minutes
cook time15 minutes
resting or cooling time10 minutes
total time40 minutes

Ingredients

Cookies

  • 1 cup salted butter, softened
  • 1 cup brown sugar
  • 1/3 cup granulated sugar
  • 2 eggs
  • 1 1/2 Tbsp corn syrup
  • 2 tsp vanilla extract
  • 2 1/2 cups all-purpose flour
  • 2/3 cup dutch processed cocoa powder
  • 2 tsp corn starch
  • 1 1/2 tsp baking soda
  • 3/4 tsp salt

Toppings

  • 1/2 cup heavy cream
  • 1 1/3 cups semi sweet chocolate chips
  • 1/4 cup rainbow coated chocolate chips

Instructions

  • Preheat oven to 350F.
  • Cream together softened butter, brown sugar, and granulated sugar until light and fluffy, about 3-4 minutes.
  • Add eggs, corn syrup, and vanilla extract. Mix until combined.
  • Add flour, cocoa powder, corn starch, baking soda, and salt. Mix until dough forms.
  • Divide dough into 9 equal portions using a 1/3 cup measuring cup.
  • Roll each portion into a ball and flatten slightly into a hockey puck shape.
  • Arrange 6 cookies per parchment-lined baking sheet.
  • Microwave heavy cream for 1 1/2 minutes until boiling.
  • Pour hot cream over semi sweet chocolate chips and let sit 3 minutes.
  • Whisk chocolate and cream until smooth. Set aside to cool.
  • Bake cookies for 15-17 minutes until centers are set and edges crinkle.
  • Cool cookies on pan for 10 minutes.
  • Spoon frosting onto each cookie and sprinkle with rainbow chocolate chips while frosting is wet.

Notes

Cookies are best served while still warm.