Preheat your oven to 350°F and line two baking sheets with parchment paper.
In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes. Beat in the egg and vanilla extract.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the butter mixture, mixing until just combined.
Fold in the white chocolate chips and dried cranberries until evenly distributed throughout the dough.
Drop rounded tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart. Gently press down on each cookie slightly—they won't spread much on their own.
Bake for 10-12 minutes, until the edges are set and just starting to turn golden. The centers will look slightly underbaked, but that's what you want for soft, chewy cookies!
Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. Store in an airtight container for up to 5 days.