Preheat oven to 350°F and line 4 sheet pans with aluminum foil, dull side up. If you don’t have 4 sheet pans, line as many as you have and plan to bake the cookies in batches.

Place butter in a medium saucepan over medium heat. Cook, swirling occasionally, until butter solids are dark brown and liquid is caramel brown, 8-10 minutes. Immediately remove from the heat and transfer to a wide, shallow heat proof pan or dish. Place in freezer to cool for 15 minutes.

In a medium bowl, whisk together flour, baking soda, and salt. Set aside.

Once butter has chilled, add it and sugars to the bowl of a stand mixer fitted with the paddle attachment, and mix on medium-high speed until lightened and fluffy, about 5 minutes. Scrape down the sides of bowl, then add egg, egg yolk, and vanilla, and beat for 1-2 minutes until well combined.

Scrape down sides of bowl once more, then add dry ingredients, and mix at low speed until just a few streaks of flour remain. Add in the chocolate chunks and mix until just combined.

Form the dough into 5, 225g (about ½ cup) balls. Place 2 balls an equal distance apart on a prepared pan and transfer to the freezer for 15 minutes before baking.

Place the first chilled pan in the oven, and place a new pan in the freezer to chill. Bake cookies for 10 minutes, until puffed in the center. Remove pan from oven and bang pan firmly onto a heatproof surface 4-5 times, until cookies spread and form a few circular wrinkles around the edges. Place back in oven, bake for another 2-3 minutes, until centers have puffed again, then repeat pan banging process. Repeat entire process two more times, for a total of 18 to 20 minutes, until the cookies have spread out, edges are golden brown and centers are underbaked.

Remove from oven and place pan on a wire rack to cool for 10 minutes, then transfer cookies to wire rack directly to cool completely.

While cookies cool, repeat process with remaining dough until all cookies are baked.