Cream together room temperature butter and sugars at medium speed in an electric mixer until light and fluffy, 2-3 minutes.
Once creamed together add in vanilla and egg, scraping the bowl after each addition.
In a separate bowl combine flour, baking soda, salt and cornstarch with a whisk or a fork.
With the mixer on low speed slowly add in dry ingredients, being careful not to over mix.
Remove bowl from mixer and add in macadamia nuts and white chocolate chunks. Using a spatula or wooden spoon carefully fold in until evenly distributed.
Using a cookie scoop shape dough into balls and place on cookie sheet. Refrigerate for at least 1 hour, up to overnight.
When ready to bake preheat oven to 350°.
Place up to 6 cookies on a parchment lined baking sheet and bake in the middle rack of the oven for 10-12 minutes. The cookies will be light in color but just set in the center. They will continue to cook for a few minutes on the hot cookie sheet when removed so air on the side of under baked.
Cool on cookie sheet for minutes and then transfer to a cooling rack to cool completely.