1. Preheat oven to 375°F. Grease cookie sheets.
2. In a large bowl, cream together butter, brown sugar and white sugar until smooth. Beat in the egg and vanilla. Combine the flour and baking soda; stir into the sugar mixture. Mix in the white chocolate chips and cranberries. Drop by heaping spoonfuls onto the prepared cookie sheets. Bake for about 8 to 10 minutes.
3. For best results, take out cookies while they are still doughy. Allow cookies to cool for 1 minute on cookie sheets before removing to wire racks to cool completely.
Makes about 2 dozen.