These chocolate-chocolate cookies with cocoa, white chocolate, and milk chocolate are seriously a triple threat. Dense, chewy, stay-soft, and perfectly sweet with a bit of salty. You'll love 'em.
In a large bowl, whisk together flour, salt, baking soda, and cocoa.
In another large bowl or the bowl of stand mixer, combine butter, both sugars, and vanilla. Beat on medium-high until it's as fluffy as it can get, scraping sides down periodically; about 3-4 minutes. Add beaten eggs and beat just to combine.
Using rubber spatula, gently fold flour mixture into butter mixture just until batter is completely moistened. Fold in all white/chocolate chips.
Wrap and chill dough until firm enough to handle, about 30 min to 1 hour.
Meanwhile, preheat oven to 350F with rack on lower middle position. Set aside parchment-lined (or silicone-lined) baking sheets.
Form dough into walnut sized balls and flatten slightly, as these tend not to spread too much. Place on parchment lined baking sheet and bake about 8 minutes. They'll seem a bit underdone, but will set up nicely when cool.