Preheat the oven to 350℉/176℃. Line your 2 baking trays with parchment paper and set aside. Melt the butter and chop the chocolate bars and set aside.
1/2 cup butter, 50 g dark chocolate, 50 g white chocolate, 50 g milk chocolate
In a medium-sized bowl, add in flour, baking soda, baking powder, cornstarch, and salt. Mix together and set aside.
1 1/2 cups all-purpose flour, 3/4 tsp baking soda, 1/4 tsp baking powder, 1/4 tsp salt, 1 tsp cornstarch
Whisk the slightly cooled melted butter, white sugar, and brown sugar in a large bowl. Then whisk in vanilla and egg.
1/2 cup butter, 1/3 cup dark brown sugar, 1/2 cup white sugar, 1 egg, 1 tbsp vanilla
Add in the dry ingredients and mix until *almost* completely combined.
Add in the chopped chocolate bars and continue mixing until just combined and no more flour streaks appear.
50 g dark chocolate, 50 g white chocolate, 50 g milk chocolate
I used a large cookie scoop. Scoop 6 cookie dough balls onto a prepared baking tray, approx 2 tbsp in size each, spacing them 1-1.5 inches apart. Add extra chocolate pieces on top if desired.
Bake the cookies for 12-15 minutes. Please make sure not to over-bake! Even if the middle looks soft and underbaked, they will continue to bake as they cool on the hot baking tray! Mine took 14 minutes exactly. Sprinkle with flakey sea salt and enjoy!