Preheat oven to 350 degrees. Line 2 cookie sheets with parchment paper.
Cream butter, sugars and peanut butter together. Mix in egg and vanilla.
In another bowl, mix together flour, baking soda, and salt. Add to butter mixture and mix until combined. Blend in 1/4 cups white chocolate chips. Scoop heaping tablespoons of dough onto cookie sheets, gently press down until 1/2 inch thick. Sprinkle with additional kosher salt if desired. Bake 12-15 minutes or until edges are golden brown.
Cool on cookie sheet for 10 minutes and then move to wire rack.
Recipe by Just Short of Crazy at http://justshortofcrazy.com/2012/12/white-chocolate-peanut-butter-cookies/