Design Eat Repeat

0 Preheat oven to 350ºF. While preheating, be sure to read tips & tricks in post above for recipe success.
1 Warm the unsalted butter ([adjustable]½ cup, i.e. 1 stick[/adjustable]) in a microwave-safe bowl or saucepan until it’s just melted.
2 In a large mixing bowl, combine the melted unsalted butter with the light brown sugar ([adjustable]½ cup) and granulated sugar (¼ cup[/adjustable]). Stir until combined. (I recommend mixing this by hand rather than a mixer.)
3 Stir in the egg ([adjustable]1 large) and vanilla extract (1 tablespoon), followed by the baking soda (½ teaspoon), baking powder (½ teaspoon), and salt (¾ teaspoon[/adjustable]). Stir in red food coloring ([adjustable]½ teaspoon[/adjustable]).
4 Mix in cocoa powder ([adjustable]3 tablespoons), cornstarch (1 tablespoon), and all-purpose flour (1 ¼ cups), followed by the white chocolate chips (1 cup[/adjustable]). Mix the dough until well-combined.
5 Generously grease a cookie cake pan. If you plan to invert the cake onto a tray (rather than serving in the pan), I highly recommend lining the bottom with parchment paper in order for the cookie cake to invert out of the pan easily.
6 Spread dough into an even layer in pan. Press in some extra chocolate chips for added presentation. Bake for 12-14 minutes, or until center looks slightly "dry" (my oven is perfect at 12 minutes). Do not overbake; it might look a little under-baked, but the residual heat from the pan will continue to bake the cookie even after you take it out of the oven.
7 Cool completely and top with cream cheese frosting. If your cookie cake is not slicing clean, refrigerate for 30 minutes to firm up.
9 To decorate, use a piping bag and large star tip to create a simple border.
To Make Frosting:
11 Beat the softened unsalted butter ([adjustable]½ cup, i.e. 1 stick), cream cheese (4 ounces), vanilla extract (2 teaspoons[/adjustable]), and a pinch of salt on medium-high speed for 1-2 minutes until smooth (it's okay if it looks a bit curdled, this will smooth out when you add the powdered sugar).Turn the mixer to low speed then add the powdered sugar 1/4 cup at a time ([adjustable]2 ½ cups[/adjustable] total). You may need to stop and scrape down the sides. Beat on high for 1-2 minutes until creamy and the frosting is at a good consistency to pipe. If it looks too runny, add more powdered sugar. If it looks too stiff, add a tiny bit of milk until you get to the desired consistency. This will make enough frosting to pipe a generous border along the edges.