How to Make It
Preheat oven to 450°.
Lightly spoon flour into dry measuring cups; level with a knife. Whisk together flour, baking soda, baking powder, and salt.
Beat butter and sugars with an electric mixer at medium speed, occasionally scraping down sides of the bowl, until light and fluffy, 2-3 minutes. Add eggs and vanilla; beat until pale, 4-5 minutes. Reduce mixer speed to low and gradually add flour mixture until just blended. Fold in chocolate chunks using a rubber spatula.
Scoop dough into even portions (2 tablespoons each) and arrange 2 inches apart on 2 parchment paper-lined baking sheets (maximum of 6 cookies per sheet). Sprinkle cookies with flaky salt and refrigerate sheets until dough is firm to touch, 10 minutes.
Bake at 450°, rotating baking sheets halfway through cooking, until just golden brown around the edges, 6-7 minutes. Let cool on baking sheets for 5 minutes, then transfer to a cooling rack. Repeat process with remaining dough.