In the bowl of a stand mixer fitted with the paddle attachment, cream together butter, light brown sugar, granulated sugar, and powdered sugar until light and fluffy, about 5 minutes.
1/2 cup unsalted butter, 3/4 cup light brown sugar, 1/2 cup granulated sugar, 1/4 cup powdered sugar
Add the egg yolks, egg, and vanilla extract and mix until incorporated. Carefully add the flour mixture to the bowl and mix until dough forms.
2 large egg yolks, 1 large egg, 1 teaspoon vanilla extract
Using a spatula, fold in the chocolate chunks.
1 cup chocolate chunks
Using a large cookie scoop, scoop dough onto prepared cookie sheets and sprinkle sea salt flakes on top.
Maldon sea salt flakes
Bake 10-12 minutes (the cookies will firm up as they cool if they still look soft to you).
Let cool for 10 minutes on the cookie sheet then transfer to a wire cooling rack to cool completely.