Preheat oven to 350F degrees. Line three large baking sheets with parchment paper.
In medium bowl, whisk together flour, baking soda, and salt. In stand mixer with fitted paddle attachment, beat butter, brown sugar, cocoa, orange zest, and vanilla on medium speed until well combined (4 minutes). Add eggs one at a time, beating briefly between additions. Add cooled chocolate and mix until blended. Add dry ingredients and mix on low speed until almost completely blended. Add chopped chocolate and mix until blended.
Shape dough into 1 1/4 inch balls with small ice cream scoop. Pour granulated sugar into shallow dish. Dip the top of each ball in sugar and set dough balls, sugar side up, about 1 1/2 inches apart on prepared baking sheets. Bake one sheet at a time until cookies are puffed and cracked on top (11 to 12 minutes). Let cookies cool on sheets for 5 minutes before transferring to rack to cool completely.
Yields about 5 dozen cookies.