In a stand mixer with the paddle attachment, mix together cold, cubed butter, and salt on medium high for 1-2 minutes. Scrape the bowl.
Add both sugars to the butter and mix on medium low for about 3 minutes scraping the bowl when necessary.
Add vanilla, then the eggs one at a time and mix on low until just combined.
In a separate bowl, mix together flour, baking soda, and cornstarch. Then add the flour mixture to the wet ingredients and mix on low, scraping the bowl when necessary.
Add in the oats, walnuts, dried cranberries, and white chocolate chips and mix on low until just combined.
Using a cookie scoop or large tablespoon, scoop out dough and place it on the prepared baking sheet.
Bake 12-15 minutes, until the edges are lightly brown but the centers still look soft.
Allow cookies to cook on the pan for 5 minutes and then transfer them to a wire rack to finish cooling.