Cosmic Brownie Cookies

If you grew up loving those fudgy cosmic brownies from the lunchbox aisle, then these Cosmic Brownie Cookies are going to be your new favorite cookie recipe. They start with my chewy double chocolate cookies and get topped with a silky chocolate ganache and rainbow chips for that classic cosmic brownie look and flavor.

 

I had to make these after I made my Cosmic Brownies because I couldn’t stop thinking about turning that nostalgic brownie into a cookie version. And honestly? These may be even better. You get all the rich fudgy chocolate flavor of a cosmic brownie but in a thick bakery-style cookie form.

I used my double chocolate chip cookies for the cookie base. Melted butter gives the cookies that chewy dense texture while brown sugar keeps them soft for days. I’ve used this base cookie for other wonderful cookies like my cookies and cream cookies made with Oreos and stuffed with white chocolate.

And nothing beats topping a dessert with ganache to give it that bakery-style finish. Like my buckeye brownie cookies and buckeye brownies! The ganache on top seals the deal and gives them that classic fudgy cosmic brownie finish.

For the cookies

• All-purpose flour: Use a kitchen scale for best results. If using measuring cups, then spoon the flour into the cup. Do not scoop directly from the bag.
• Dutch process cocoa powder: Use Dutch process cocoa powder, not regular unsweetened cocoa powder for a richer, more intense chocolate flavor.
• Cornstarch: Helps create a softer, chewier cookie texture. Don’t skip it!
• Baking soda
• Salt
• Unsalted butter: Melting the butter helps create a chewy cookie. If using salted butter, then reduce the added salt.
• Light brown sugar: If you run out use my homemade brown sugar recipe. You can also use dark brown sugar.
• Granulated sugar
• Eggs: Room temperature eggs mix more evenly into the dough. Place in a bowl of warm water for 10 minutes before using.
• Vanilla extract
• Semi-sweet chocolate chips: You can also use chopped chocolate or milk chocolate chips

For the ganache topping

• Heavy cream: Do not substitute with milk.
• Semi-sweet chocolate: Or high quality chocolate chips
• Rainbow chips: the classic cosmic brownie finishing touch

How To Make Cosmic Brownie Cookies

Begin by whisking together the dry ingredients in a large mixing bowl. You want to evenly distribute the cocoa powder, cornstarch, baking soda, and salt throughout the flour before adding them to the wet ingredients. This helps prevent overmixing later and ensures the cookies bake evenly.

In a separate bowl, whisk together the melted butter, brown sugar, and granulated sugar. Since the butter is melted instead of softened, the mixture should look smooth and glossy. Melted butter helps create a dense chewy texture that works perfectly for brownie-style cookies.

Add the eggs and vanilla extract and whisk until fully combined. Make sure your eggs are at room temperature so they incorporate smoothly into the butter mixture without causing it to seize up.

Stir the dry ingredients into the wet ingredients just until combined. The dough will be thick. Once you still see a few streaks of flour remaining, fold in the chocolate chips. Avoid overmixing here or the cookies can become tough.

You need to chill the dough so the cookies don’t spread too much in the oven. You can either scoop the dough before or after chilling. I like to scoop before because it’s easier. You want to scoop using a #20 cookie scoop (about 3 Tablespoons each) and place onto the parchment paper lined cookie sheet. Then cover with plastic wrap and chill for at least 2 hours.

This step is important because the melted butter creates a softer dough that needs time to firm up. Chilling also helps deepen the chocolate flavor.

When ready to bake, if you need to scoop then let the dough sit at room temperature for a few minutes if it feels too firm to scoop.

Preheat the oven to 350°F (177°C). Line baking sheets with parchment paper.

Place the cookies about 2 inches apart on the prepared baking sheets since they will spread as they bake.

Bake on the center rack for 10–12 minutes. The edges should look set while the centers will still appear slightly soft and puffy. The cookies will continue to bake as they cool on the baking sheet, so avoid overbaking them if you want a fudgy texture.

As soon as the cookies come out of the oven, use a large round cookie cutter or drinking glass to gently swirl around the cookies to shape them into perfect circles. This is one of my favorite tricks for bakery-style cookies.

If desired, press a few extra chocolate chips into the tops while the cookies are still warm for a prettier finish.

Let the cookies cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely.

To make the ganache, heat the heavy cream in a microwave-safe bowl until steaming hot but not boiling. This usually takes about 30 seconds to 1 minute depending on your microwave.

Add the chopped chocolate and let it sit undisturbed for about 3 minutes. This allows the heat from the cream to gently melt the chocolate without overheating it. Stir until smooth and glossy.

Spread the ganache over each cooled cookie and immediately sprinkle with rainbow chips before the ganache sets.

Storage

Store the cookies in an airtight container at room temperature for up to 4 days. Because of the ganache topping, I like to place parchment paper between layers so they don’t stick together.

You can freeze the baked cookies for up to 3 months. Let the ganache fully set first, then place the cookies in a freezer-safe container or bag with parchment paper between layers.

To freeze the cookie dough, scoop the dough into balls and place on a parchment-lined baking sheet. Freeze until solid, then transfer to a freezer bag or airtight container. I recommend labeling the bag with the recipe name, baking temperature, and baking time so it’s easy to grab later.

To bake from frozen, place the frozen cookie dough balls directly onto a prepared baking sheet and bake at 350°F. Add an extra 1–2 minutes to the baking time. No need to thaw the dough first.

More Recipes To Try

If you’re in a cookie baking mood, I have plenty more cookie recipes to add to your baking list next. My Old-Fashioned Peanut Butter Cookies and no bakes are two of my favorite nostalgic recipes.

If you love bright citrus desserts, my Lemon Cookies topped with a sweet lemon glaze or my key lime cookies made with fresh lime zest and lime juice.

For something extra fun, try my Cookie Dough Cookies which are topped with edible cookie dough in the center.