Meanwhile, whisk together the whole egg, the egg yolk, milk and vanilla extract in a measuring cup. Reduce the mixer speed and slowly add the egg mixture. Mix until thoroughly combined, about 30 seconds.
Using the paper plate as a slide, gradually integrate the dry ingredients, stopping a couple of times to scrape down the sides of the bowl. Once the flour is worked in, drop the speed to stir and add the chocolate chips. Chill the dough for 1 hour.
Preheat the oven to 375 degrees F and place racks in the top third and bottom third of the oven.
Scoop the dough into 1 1/2-ounce portions onto parchment-lined half sheet pans, 6 cookies per sheet. Bake 2 sheets at a time for 15 minutes, rotating the pans halfway through. Remove from the oven, slide the parchment with the cookies onto a cooling rack and wait at least 5 minutes before devouring.
The darker the sugar you use, the chewier your cookies will be.