In a large bowl, whisk together the sugars, kosher salt and butter until a smooth paste forms with no lumps.
Whisk in the egg and vanilla, beating until light ribbons fall off the whisk and remain for a short while before falling back into the mixture. This will look like a granulated caramel.
In a separate bowl, sift in the flour, baking soda and milk powder. Then fold the mixture with a spatula (Carefully not to over mix).
Fold in the chocolate chips or chunks, then cover and chill the dough in the fridge for at least 30 minutes. For a more intense toffee-like flavor and deeper color, chill the dough overnight. The longer the dough rests, the more complex its flavor will be. You can also scoop the cookies at this point and freeze to bake as needed or later.
Preheat oven to 350°F. Line a baking sheet with parchment paper or spray with cooking spray.
Scoop the dough with an ice-cream scoop onto a parchment paper-lined baking sheet, leaving at least 4 inches of space between cookies and 2 inches of space from the edges of the pan so that the cookies can spread evenly.
Bake for 12-15 minutes, or until the edges have started to barely brown. If your oven bakes hotter, check at the 12 minute mark. Cool the cookies and Enjoy!
