Preheat oven to 350°F and line two baking sheets with parchment paper.
In a large bowl, beat together butter and sugars until light and fluffy. Beat in egg and vanilla until smooth.
In another bowl, sift together flour, baking soda, and salt. Mix into the wet ingredients, stopping halfway through mixing to add in the white chocolate and cranberries. Continue to mix until dry ingredients are fully incorporated.
Use a large cookie scoop (3 tablespoons) to scoop cookie dough onto prepared baking sheets, leaving space between cookies to allow for spreading.
Bake for about 16 minutes, until edges are golden brown. Let cool on the baking sheet for 2 minutes, then remove to a wire rack to cool completely.
Notes
To make smaller cookies, use a medium (1 1/2 tablespoons) cookie scoop. Bake for 10-12 minutes.