Preheat the oven to 350 F.

Chop the bittersweet chocolate and melt it, either in microwave on 50% power or in double boiler. Set aside.

Whisk together the flour, cocoa powder, baking soda and salt. Set aside.

Using a mixer, beat the butter until creamy. Scrape the sides and bottom of the bowl and add the sugar. Beat until light and fluffy, about 3 minutes on a higher speed. Beat in the vanilla.

Scrape the sides and bottom of the bowl again, and now add the melted and cooled chocolate. Beat until incorporated. Beat in the eggs, one at a time, scraping the bowl as needed.

Slowly mix in the flour mixture and then slowly mix in the chocolate chips.

If desired, you can store the dough in the fridge at this point for up to 3 days. But if baking now, use a small-medium cookie scoop to create about 2 tablespoons sized balls of dough. Bake 6 cookies to a sheet--what you lose in convenience you will gain in air circulation around each individual cookie.

Bake for 9-10 minutes, until cookies are set at the edges but look slightly underdone still.

Let cookies cool for 10 minutes on the cookie sheet before transferring to a cooling rack.