Line two rimmed baking sheets with parchment paper. Using a stand mixer fitted with the paddle attachment or an electric hand mixer, beat the butter, both sugars and vanilla on medium-high till it’s super light and fluffy (3 to 5 minutes for a stand mixer; 6 to 8 for a hand mixer). Using a spatula, scrape down the sides of the bowl and, with the mixer on low, slowly add the flour, followed by the chocolate chunks, and mix just to blend. If necessary, knead the dough with your hands to make sure the flour is totally incorporated. At this point, the dough should be smooth and feel like Play-Doh with no pockets of flour.