In a mixer bowl fitted with the paddle attachment, beat the butter on medium speed for 30 seconds until creamy. Add sugars, salt, and vanilla and beat for 2 more minutes until smooth.
Add flour mixture and grated chocolate, and beat on low speed just until combined and the mixture is crumbly with large pieces of dough. Work the dough as little as possible, being careful not to over mix.
Preheat oven to 350℉/180℃. Line 2 pans with parchment paper.