Heat oven to 375°F and place the racks in the top third and bottom third of the oven. Line 4 half-sheet pans with parchment paper and set aside.
Melt the butter in a 2-quart saucepan over low heat. Set aside to cool slightly.
Sift together the flour, salt, and baking soda onto a paper plate.
Pour the butter into the bowl of your stand mixer. Add the sugars and beat with the paddle attachment on medium speed for 2 minutes.
Meanwhile in a separate bowl, whisk together the whole egg, egg yolk, milk, and vanilla extract.
Slow the mixer to “stir” and slowly work the egg mixture into the butter and sugar. Mix until thoroughly combined, about 30 seconds.
Using the paper plate as a slide, gradually integrate the dry ingredients, stopping a few times to scrape down the side of the bowl with a rubber spatula. Once the flour is worked in, add the chocolate chipsI'd suggest chopping your own dark chocolate chunks in the 68% cocoa range.. Chill the dough for 1 hour.
Scoop the dough into 1 1/2-ounce portions and place on the half-sheet pans, 6 cookies per sheet.
Bake two sheets at a time for 15 minutes, rotating pans halfway through baking.
Remove from the oven, slide the parchment with the cookies onto a cooling rack, and wait at least 5 minutes before devouring.