1-Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper on light-colored metal pans for even baking.

2-In a large bowl, mix softened butter, light brown sugar, and granulated sugar with an electric mixer on medium-high speed for 2 minutes until light and fluffy. Softened butter ensures the best dough consistency.

3-Add the egg, vanilla extract, and light corn syrup. Mix on low speed until combined, scraping down the sides as needed.

4-Add baking soda and salt. Mix briefly until combined.

5-Add dark cocoa powder and all-purpose flour. Mix on medium speed until a thick dough forms.

6-Scoop dough into ¼ cup portions, roll into balls, and gently flatten to about ½ inch thickness. This step encourages spreading and prevents puffiness.

7-Bake for 11-12 minutes. Centers may look slightly wet but will firm up as cookies cool. Let cool completely on the pan before decorating.

8-Place ¾ cup semi-sweet chocolate chips in a heat-safe bowl.

9-Heat ¼ cup heavy cream in the microwave for 30-45 seconds until hot but not boiling.

10-Pour the hot cream over the chocolate chips without stirring initially. Press chips to submerge.

11-Let sit for 3 minutes, then stir until smooth and creamy. Reheat briefly if needed.

12-Spoon about 1 tablespoon of ganache on each cooled cookie, then add rainbow chip sprinkles or alternatives like mini chocolates or colored sprinkles.

13-Refrigerate for 30-60 minutes to set the ganache.