Preheat oven to 350 degrees.
In a bowl, mix flour, cocoa powder, baking soda and salt.
In the bowl of your stand mixer, with the paddle attachment, beat sugars and butter until smooth. Beat in egg and vanilla extract. Add flour mixture and beat until smooth. Fold in white chocolate chips.
Drop rounded tablespoons of dough onto a lightly greased or parchment paper lined cookie sheet.
Bake in preheated oven for 10-12 minutes until toothpick runs through the cookie clean.
Transfer cookies to cooling rack.