Mix flour, cornstarch and salt with a whisk in a small mixing bowl.
Add the butter and sugar to a medium-sized mixing bowl, cream together using an electric hand mixer, about 1 to 2 minutes. Add vanilla extract and mix thoroughly.
Adding mixed dry ingredients in two batches to the wet ingredients, mix until ingredients are combined (with hand mixer) but don’t over mix. Add the cranberries and chopped white chocolate to the cookie dough and mix with rubber spatula.
Split cookie dough in half. Add first half to a long pieces of plastic wrap. Shape into 7 to 8-inch logs that are about 1 1/2 inches thick.
Once shaped, wrap with another piece of plastic and place in the refrigerator for at least 3 hours or overnight.
Heat oven to 350 degrees F. Cut into 1/4 or 1/2 inch thick slices and place on parchment paper lined baking sheets for 10 to 11 minutes.
Notes
Notes: Make the dough ahead of time and freeze it. Make the dough ahead and freeze the logs. Slice the cookies and bake (you might need to bake the cookies a couple minutes longer if baking them straight from the freezer).
Optional: You can dip them in melted white chocolate too! Melt 3/4 cup chopped white chocolate along with 3 to 4 teaspoons vegetable shortening in a microwave safe bowl on 50% power for 30 seconds and then 15 seconds at a time after that until it’s melted. Be sure to mix with a spoon after each interval. Dip cooled shortbread cookies halfway in the white chocolate and place on a parchment paper lined baking sheet. Place in the fridge for at least 15 minutes to set.