Measure the butter into a small pan and set over low heat until melted. Remove from the heat and set aside to cool. In a medium bowl, sift together the flour, salt and baking soda and set aside.
In a mixing bowl fitted with a paddle attachment, beat the melted butter together with both the granulated and light brown sugars. Turn to medium and beat for about two minutes.
Meanwhile, in a small bowl, whisk together the egg, yolk, whole milk and pure vanilla extract. Turn the mixer to low and add the egg mixture. Beat until the mixture is becomes quite thickened and creamy. Don't skip this step!
Turn the mixer to low and slowly add in the sifted flour mixture until it is all incorporated.
Remove from the mixer and stir in the chocolate chips.
Cover with a tea towel or plastic wrap and put your mixing bowl in the fridge and let it sit there for one whole hour. This is a key step, if you do not do this the already melted butter in the cookie dough will cause the cookies to immediately flatten once in the oven. So, into the fridge your dough must go.
After one hour, preheat the oven to 375F.
Remove the dough from the fridge and scoop onto either a parchment or silpat lined cookie sheet. Bake for about 12-14 minutes, rotating the pan halfway through. The cookies are done when they're slightly browned. Transfer to a wire rack to cool.
Store in an airtight cookie jar or container.
Notes
I made a few larger cookies and gave them a little pat down before baking.
Recipe by Just a Smidgen at https://justasmidgen.com/2014/07/10/alton-browns-chewy-chocolate-chip-cookie-recipe/