In a large mixing bowl fitted with a paddle attachment, cream the butter until light and fluffy.. Add the sugar and beat on medium-high until fully blended. Scrape down the sides.
Add the large egg and vanilla and beat until light and fluffy, about 4 minutes. Scrape down the sides again. Add the two types of flour, the baking soda and the salt. Turn on medium-high and mix until the flour is fully worked in.
Add the cranberries, white chocolate chunks and walnuts. Either blend on low or fold by hand until everything is mixed together. If the dough is too loose, add an additional 1/4 cup flour. Place the dough in the fridge for at least one hour.
Preheat oven to 350F.
Scoop in small spoonfuls (about 2 tablespoons) onto a parchment or silpat lined cookie sheet.
Bake for about 9 minutes, only until the edges of the cookie are slightly browned. This leaves the centers soft and fluffy once they cool. Allow them to begin cooling right on the cookie sheet, then gently transfer them to a wire rack to finishing cooling down.
This dough may be sealed in a sealed container in the fridge for up to 5 days.