Preheat oven to 350 degrees F. Line a baking sheet with parchment paper, set aside.
With the paddle attachment, beat together the butter, sugar, vanilla and salt until light and fluffy.
Add the egg whites one at a time and beat until smooth between each addition about 2 minutes. This is important, if you add them all at once, your egg whites will not combine properly into batter.
Beat in the cocoa, mix until just combined. Add flour and baking soda and mix. Fold in the chocolate chunks. Do not overmix.
Scoop cookie dough balls in about 2-3 tablespoons onto a parchment lined cookie sheet. Sprinkle with more chopped white chocolate.
Stick the pan in the freezer for about 5-8 minutes then put it straight into the oven.
Bake for 10 minutes and repeat with remaining dough. Allow cookies to fully set before moving off of pan - about 5 minutes. When you bake them, bake for no longer than 10 minutes.