1. Preheat oven to 375 degrees F (190 degrees C).
2. In a large bowl, using an electric mixer, cream together butter, white sugar and brown sugar.
3. Add egg and vanilla extract, mix well (scraping down the sides and bottom of the bowl). Combine flour, baking soda and salt, stir gradually into the creamed sugar mixture.
4. Add white chocolate chips and stir.
5. Stir in cranberries.
6. Line a baking sheet with parchment paper (I had 2 baking sheets).
7. Drop by heaping spoonfuls onto the prepared baking sheet (leave some space between the cookies).
8. Bake for 8 minutes, until barely golden brown around the edges (you need to watch them closely, the cookies will look undone in the center when you remove them from the oven, but they will firm up when cooling on the baking sheet).