Preheat your oven to 350 degrees Fahrenheit. Line two baking sheets with parchment paper and set them aside for later use. In your stand mixer bowl, combine the softened butter, brown sugar, and granulated sugar. Cream these ingredients together for approximately 2 minutes until the mixture becomes smooth and well combined.

Add the vanilla extract, eggs, and corn syrup to the butter mixture. Mix everything together thoroughly until fully incorporated.

Incorporate the cocoa powder, flour, baking soda, cornstarch, and salt into the wet ingredients. Mix the dough completely, making sure to scrape down the sides of the bowl frequently to ensure all ingredients are evenly distributed.

Fold the chocolate chips into the dough until they're spread throughout the mixture evenly.

Using a large ice cream scoop, portion the dough and place the portions onto your prepared baking sheets, leaving space between each cookie for slight spreading.

Bake the cookies in the preheated oven for approximately 10 minutes, or until the centers appear set when you gently shake the pan. Allow the cookies to cool completely on the baking sheets before adding frosting.

For the frosting, combine the softened butter and cream cheese in your stand mixer bowl. Cream them together until the mixture becomes smooth and fluffy.

Add the cocoa powder, vanilla, and approximately half of the powdered sugar to the butter mixture. Mix everything on low speed until the ingredients come together.

Pour in the remaining powdered sugar and mix on low speed until combined. Increase the mixer speed to medium and whip the frosting for about one minute until it becomes smooth and fluffy, scraping down the sides often. Transfer your finished frosting to a piping bag fitted with a large star tip.

Once the cookies have cooled completely, pipe a decorative spiral of frosting on top of each cookie, starting from the outer edge and working your way to the center.