In a small bowl, using a hand mixer, beat the butter, sugar, vanilla and salt for 2-3 minutes.
Add the egg white and beat for one minute.
Add the baking soda, flour and dutch process cocoa and beat to combine.
Fold in the chopped chocolate (including the small bits!).
Cover the bowl with plastic wrap and set in the fridge overnight, or at least four hours.
Preheat oven to 350. Prepare a cookie sheet with parchment paper.
Drop cookies by a heaped 1 1/2 tablespoon onto cookie sheet.
Sprinkle with sea salt and stick the tray in the freezer for 5-10 minutes (this to help minimize spreading).
Bake for 13 minutes, let completely cool before moving.