Preheat the oven to 350 F. In a large bowl, mix together butter and powdered sugar until fluffy. Add in the vanilla extract, and mix until smooth.
Add in the flour and cocoa powder, mix until it is fully combined. Fold in the white chocolate chips. Roll the cookie dough into balls, and flatten each one slightly. Place the cookies onto a large ungreased baking sheet. Bake for 10-12 minutes.