In a large bowl beat together the melted butter and sugars.
Beat in the egg, egg yolk, and vanilla extract.
In a separate bowl whisk together the flour, cornstarch, baking soda and salt.
Beat the flour mixture into the butter mixture about ½ at a time.
Turn off the mixer and gently fold in the macadamia nuts and chocolate chips (I usually reserve a tablespoon or 2 of each for dotting the tops of the cookies after baking).
Cover the bowl, and refrigerate for at least 2 hours or overnight.
When ready to bake, preheat the oven to 350F degrees and line cookie sheets with parchment paper or baking mats.
Take the dough out of the fridge to soften slightly for 5-10 minutes (or 15 minutes if dough has been in the fridge overnight).
Using a cookie scoop, form the dough into balls about the size of a golf ball (about 1 - 1.5 tablespoons in size), and place 2 inches apart on the lined cookie sheets.
Bake 1 sheet at a time on the middle rack of your oven for 8-10 minutes, or until the tops are just set.
Remove from the oven, optionally place a few chocolate chips & macadamias on the top of each cookie. Cool on the cookie sheet for at least 10 minutes, then transfer to a wire rack to continue cooling.