Brown the butter
Melt 1 cup unsalted butter in a light-colored saucepan over low heat, then increase to just above medium, stirring constantly until the foaming subsides and the milk solids brown. Immediately remove from heat and scrape into a bowl.
Cool the butter
Let the brown butter cool until it is no longer warm to the touch, ideally room temperature but still slightly liquid.
Mix in the sugars
Stir 1 cup firmly packed brown sugar (a blend of light and dark for best flavor) and 2/3 cup granulated sugar into the cooled brown butter.
Add eggs and vanilla
Mix in 2 room-temperature large eggs and 1 1/2 teaspoons vanilla extract until well combined.
Whisk dry ingredients
In a separate bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt.
Combine and fold in chocolate
Gradually add the dry ingredients to the wet in about four additions until no dry streaks remain, then fold in 10 ounces of chopped semi-sweet chocolate.
Chill the dough
Cover and refrigerate the dough for 30 minutes to firm up and develop flavor. Preheat the oven to 350°F (175°C).
Scoop and shape
Scoop 2 tablespoon (about 50 g) portions, roll into smooth balls, and place at least 2 inches apart on a baking sheet.
Bake
Bake one tray at a time on the center rack for 10 to 12 minutes, until edges are lightly golden but centers look slightly underdone.
Finish with flaky salt
While the cookies are still warm, sprinkle with flaky Maldon sea salt and let cool completely on the baking sheet.
Brown the butter
Melt 1 cup unsalted butter in a light-colored saucepan over low heat, then increase to just above medium, stirring constantly until the foaming subsides and the milk solids brown. Immediately remove from heat and scrape into a bowl.
Cool the butter
Let the brown butter cool until it is no longer warm to the touch, ideally room temperature but still slightly liquid.
Mix in the sugars
Stir 1 cup firmly packed brown sugar (a blend of light and dark for best flavor) and 2/3 cup granulated sugar into the cooled brown butter.
Add eggs and vanilla
Mix in 2 room-temperature large eggs and 1 1/2 teaspoons vanilla extract until well combined.
Whisk dry ingredients
In a separate bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt.
Combine and fold in chocolate
Gradually add the dry ingredients to the wet in about four additions until no dry streaks remain, then fold in 10 ounces of chopped semi-sweet chocolate.
Chill the dough
Cover and refrigerate the dough for 30 minutes to firm up and develop flavor. Preheat the oven to 350°F (175°C).
Scoop and shape
Scoop 2 tablespoon (about 50 g) portions, roll into smooth balls, and place at least 2 inches apart on a baking sheet.
Bake
Bake one tray at a time on the center rack for 10 to 12 minutes, until edges are lightly golden but centers look slightly underdone.
Finish with flaky salt
While the cookies are still warm, sprinkle with flaky Maldon sea salt and let cool completely on the baking sheet.