Preheat: Preheat the oven to 350°F and spray an 8x8 or 9x9 baking dish with baking spray.
Beat butter + sugars: Beat butter, brown sugar, and granulated sugar for 2–3 minutes until combined. Since the butter is cold, it will look more like a paste (rather than light and fluffy) Start Timer
1/2 cup unsalted butter, 2/3 cup packed brown sugar, 1/4 cup granulated sugar
Add eggs + vanilla: Mix until smooth and fully combined.
1 large egg, 1 large egg yolk, 1 tsp. vanilla extract
Whisk dry ingredients: Whisk flours, cornstarch, baking soda, baking powder, and salt in a separate bowl.
1¼ cups all-purpose flour, spooned and leveled, 3/4 cup cake flour, spooned and leveled, 1 tsp. cornstarch, 1/2 tsp. baking soda, 1/2 tsp. baking powder, 1/2 tsp fine salt
Combine ingredients: Add to wet ingredients and mix just until combined.
Add chocolate: Mix in super cookie chips and milk chocolate chips.
1/2 cup super cookie chips, 1/2 cup milk chocolate chips
Scoop: Divide the cookies into 6 large cookie balls and place in the prepared dish. Press extra chocolate chips on top for a bakery look.
Extra chips for pressing on top, optional
Bake: Bake at 350°F for ~19-21 minutes until the tops are golden, but the cookie will still be a bit underbaked. That’s what we want! They will continue to set as they cool. Start Timer
Cool and serve: Allow to cool for a few minutes (if you can wait!). Garnish with some Maldon flaky sea salt. Scoop and serve with ice cream. Note: cookies will be very gooey straight out of the oven, and will set up a lot more as it cools.