Make the Kroll's Kookies (Chocolate Chip Cookie Dough). Place cookie dough in the fridge. Kroll's Kookies
Make the brownie cookie batter next. Combine dry ingredients in a medium sized bowl: flour, cocoa powder, cornstarch, baking powder and salt. Whisk and set aside.
1 3/4 cups All-Purpose Flour, 1/4 cup cocoa powder, unsweetened, 1 tsp. baking powder, 1 tsp. cornstarch, 1/2 tsp. salt
Melt 4 oz. chocolate chips and butter in a small saucepan over medium-low heat. Stir just until ingredients are melted and be careful to watch so chocolate doesn't burn. Remove from heat, stir in vanilla extract and cool. (You can also melt this in the microwave in 30 second increments).
8 Tbsp. unsalted butter, 8 oz. chocolate chips, ~1 cup, divided, 1 tsp. vanilla extract
Whisk the eggs and sugars using a stand-mixer fitted with the whisk attachment for 3-4 minutes or until thick and pale in color. Remove mixing bowl from stand mixer.
2 large eggs, room temperature, 3/4 cup brown sugar, packed (light or dark), 1/4 cup white sugar
Stir in the cooled chocolate mixture using a rubber spatula until well combined.
Add in flour mixture and remaining chocolate chips and fold until combined, avoid over-mixing. Dough will look shiny.
Place brownie cookie dough in the fridge for 15 minutes.
Preheat oven to 400°F. Line 2 baking sheets with parchment paper or silicone baking mats.
Remove chocolate chip cookie dough from the fridge and using a food scale, weight out 1.25 oz. portions (or as small as .5 oz.) and roll into small balls. Place on the baking sheets or a large plate and repeat with remaining dough. (If you don't have a food scale, each ball is ~ 1 1/2 Tbsp.)
Repeat same process for the brownie cookie dough.
Layer a chocolate chip cookie ball, then a brownie ball, then chocolate chip then brownie together. (Each cookie will have 2 chocolate chip balls and 2 brownie batter balls)
Roll these portions together into a ball so they slightly marble into each other. Split the ball of dough in half and rotate on of the halves vertically 180 degrees and then roll the ball back together between the palms of your hands. (See the video tutorial for guidance). Repeat with remaining dough. Will make ~13-14 large cookies or you can make them smaller 2 oz. cookies.
Place cookies on prepared baking sheets and bake for 10-11 minutes. Allow to cool on cookie sheet for 10-15 minutes before transferring to a cooling rack to cool completely.