In a large bowl, combine the dry ingredients. Mix together the flour, baking soda, cornstarch, and salt. Set aside.
In a large bowl with a hand mixer or in a stand mixer with a paddle attachment, cream the butter on medium speed, about 1 minute. Then add the sugars and continue to mix, about 3-4 minutes until the butter is a pale yellow. Then add in the egg and vanilla. Make sure everything is fully mixed together.
Add the dry ingredients to the butter mixture. Add the ingredients in two parts so it will be less messy. Mix fully to combine. You may need to scrape down the sides of the bowl as you go.
When the mixture is fully combined, add in the dried cranberries and white chocolate chips. Mix for less than 1 minute to combine.
Prepare a sheet pan with parchment and scoop the cookie dough balls on it. The cookie dough balls should be about 1 tablespoon big. Don't worry about crowding the pan with cookie dough as they as not going in the oven right away.
Chill the dough. Wrap the dough on the sheet pan with plastic wrap and place in the refrigerator for 2 hours or up to 2 days.
After chilling the cookie dough, let the cookies sit out for about 5-10 minutes. Preheat the oven to 350 and line two cookie sheets with parchment.
Space the cookies about 2 inches apart and place in the oven. Bake for 8 minutes.
Let the cookies cool on the pan until they are cool enough to move to a wire rack.
The cookies will last about a week in an airtight container. They can be frozen as well for up to 3 months.
If you want to premake the cookie dough and freeze it, freeze the dough in cookie dough balls. Place the cookie dough balls in a ziplock bag and freeze for up to 3 months