Preheat the oven to 350°F (convection). Line an 8×8-inch square pan with parchment paper and set aside.

In a medium bowl, mix together the room-temperature cream cheese, powdered sugar, and vanilla extract until smooth. Set aside.

In a large bowl or stand mixer fitted with the whisk or paddle attachment, beat the room-temperature butter, granulated sugar, and brown sugar until light and off-white in color, about 1–2 minutes.

Add the egg, vanilla extract, and corn syrup, mixing until fully combined.

Add the all-purpose flour, black cocoa powder, baking powder, and baking soda. Gently fold the dry ingredients into the dough until no dry spots remain.

Press about ⅔ of the cookie dough evenly into the prepared pan.

Spread the cream cheese mixture over the dough in an even layer. Drop the remaining cookie dough over the top in chunks (it does not need to fully cover the surface).

Sprinkle with extra granulated sugar, if desired.

Bake for 30–32 minutes, until the edges are set and the center is just set.

Allow the cookie bars to cool and chill for 45–60 minutes before slicing into 3×3 bars.

Enjoy fresh, or store in an airtight container in the refrigerator for up to 8 days.