1-Preparing the Cookie Dough: First, preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper for easy cleanup. Using parchment paper is essential for preventing the cookies from sticking and makes transferring them after baking much simpler.

2-Preparing the Cookie Dough: In a large mixing bowl, cream the softened butter with the light brown sugar and granulated sugar using an electric mixer on medium-high speed. Continue beating until the mixture is light and fluffy, which should take about 2 minutes. This process is crucial for incorporating air into the dough and creating a lighter texture in the final cookie.

3-Preparing the Cookie Dough: Next, add the egg, vanilla extract, and light corn syrup to the creamed mixture. Mix on low speed until just incorporated, then scrape down the sides of the bowl to ensure all ingredients are evenly combined. This step helps prevent overmixing, which can develop gluten and make the cookies tough instead of fudgy.

4-Preparing the Cookie Dough: Now add the baking soda and salt, mixing briefly to distribute them evenly. The baking soda will help the cookies maintain their structure without causing them to puff up too much during baking.

5-Preparing the Cookie Dough: Gradually add the dark cocoa powder and all-purpose flour, mixing until fully combined. The dough will be quite thick and glossy due to the dark cocoa powder and corn syrup. Avoid overmixing at this stage to maintain the tender texture of the cookies.

6-Shaping and Baking the Cookies: Scoop the dough into ¼ cup portions, roll them into balls, and gently flatten each into about ½ inch thick discs. This flattening step is crucial to prevent the cookies from becoming too puffy during baking. For smaller cookies, reduce the dough scoop size and adjust the baking time accordingly.

7-Shaping and Baking the Cookies: Place the shaped dough discs on your prepared baking sheet, leaving enough space between them for slight spreading. For best results, use light-colored metal baking pans lined with parchment paper to prevent overbrowning and help maintain softness.

8-Shaping and Baking the Cookies: Bake the cookies for 11-12 minutes. You might notice they appear slightly wet in the center when you first remove them from the oven this is perfectly normal and desirable for a fudgy texture. The cookies will firm up as they cool.

9-Making the Ganache Topping: While the cookies are cooling, prepare the ganache topping. Place the semi-sweet chocolate chips in a heat-safe bowl. Heat the heavy cream until it bubbles slightly, which should take approximately 30-45 seconds in the microwave or on the stovetop.

10-Making the Ganache Topping: Pour the hot cream over the chocolate chips without stirring initially. This allows the heat to begin melting the chocolate gradually. Let the mixture sit for 3 minutes to give the chocolate time to soften.

11-Making the Ganache Topping: After the resting period, stir the mixture until it becomes smooth and creamy. If the chocolate isn’t completely melted, you can reheat the mixture in 10-second intervals in the microwave, stirring after each heating. The resulting ganache should be glossy and thick enough to hold its shape when spread.

12-Decorating and Finishing: Once the cookies have cooled completely, spread approximately 1 tablespoon of ganache on each cookie. You can use the back of a spoon or an offset spatula to create a smooth, even layer.

13-Decorating and Finishing: Immediately add rainbow chip sprinkles or your preferred toppings while the ganache is still slightly tacky. This ensures the toppings adhere properly. The colorful sprinkles are what give these cookies their cosmic appearance and add a delightful crunch to complement the fudgy texture.

14-Decorating and Finishing: Refrigerate the cookies for 30-60 minutes to let the ganache harden properly. This step not only sets the ganache but also helps develop the cookies’ fudgy texture. After chilling, these fudgy cosmic brownie cookies can be stored chilled for best texture and flavor or kept at room temperature for up to 2 days.