Preheat the oven to 350℉/176℃. Line your 2 baking trays with parchment paper and set aside.
Brown the butter: Melt the butter in a medium sized pan over medium heat. Once it melts, it will crackle, then become foamy – continue mixing the butter while this happens to prevent burning. The butter will go from melted to golden brown quickly, and you’ll know it’s almost done when the aroma of browned butter arrives. The whole process should take about 5 minutes! Once golden, remove from heat and transfer to a glass bowl to cool as you measure out the rest of your ingredients. (Cool for 15-20 minutes).
1/2 cup + 1 tbsp unsalted butter
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 tsp cornstarch, 1/4 tsp salt
Into a large bowl whisk the slightly cooled brown butter, white sugar, and brown sugar in a large bowl. Then whisk in vanilla and egg until well combined and the mixture is lighter in colour.
1/2 cup + 1 tbsp unsalted 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 chopped, 50 g white chocolate chopped, 50 g milk chocolate chopped
I used a large cookie scoop. Scoop the cookie dough balls on the 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!