Preheat the oven to 350F then line a baking sheet with parchement paper and set it aside.
Cream the butter, granulated sugar, and brown sugar together until smooth and creamy.
½ cup butter, ⅔ cup brown sugar, ½ cup granulated sugar
Whisk in the egg, vanilla extract, vinegar, and red gel food coloring until combined.
1 egg, 1 teaspoon vanilla extract, 1 teaspoon white vinegar, 1-2 teaspoon red gel food coloring
Mix in the flour, cocoa powder, cornstarch, baking powder, and salt until the flour mixture disappears. Don't overmix your dough. Save one tablespoon of cookie dough to decorate your cookies later.
¼ cup cocoa powder, 1 & ¾ cup all purpose flour, ¼ teaspoon salt, 2 tablespoon cornstarch, ½ teaspoon baking powder
Then using a large cookie scooper scoop out 9 equally sized cookie dough balls, place them on the prepared baking sheet, and gently flatten them to about ½ inch in thickness. Bake the cookies in the oven for 10 minutes, then let them cool down on the baking sheet for 10-15 minutes before transferring to a cooling rack to cool down fully.
Bake the 1 tablespoon of cookie dough for 7-8 minutes then use it to decorate the cookies.