These cookies have a lot of flair--they're deeply chocolatey, with both cocoa and chocolate pieces; can be made ahead (freeze the balls already rolled in confectioners' sugar, then bake whenever you're ready), and have an unexpected hint of orange blossom flavor (to substitute orange blossom water, just leave out and increase vanilla to 2 teaspoons).
Beat the butter in a stand mixer fitted with the paddle attachment until smooth. Add the granulated and brown sugars and beat again at medium speed until light and fluffy, about 2 minutes.
Add the eggs one at a time, beating well after each addition. Add the vanilla and orange blossom water and beat until combined.
In a medium bowl, whisk the flour, cocoa powder, baking powder, and salt. Add the flour mixture and the chopped chocolate to the butter mixture and beat on low speed until moistened, then on medium speed until combined. Scrape down the sides of the bowl as needed.
Chill the dough, covered, for at least one hour and up to one day.
Heat the oven to 350 degrees if baking the cookies right away. Line 2 sheet pans with parchment or silpats. Put the confectioners' sugar in a small bowl.
Make the dough balls by pulling off about a tablespoon of dough for each ball by hand, or using a tablespoon scooper. Shape the ball between the palms of your hand, then roll heavily in the confectioners' sugar (shake off excess if needed).
If freezing the dough for later, place the balls in a single layer on a sheet pan or platters that will fit in the freezer. Freeze, then put the balls into ziploc bags and freeze for up to 3 months. Bake from frozen in preheated oven following the directions below, adding to baking time by a minute or two.
Place the coated balls about 2 inches apart on the lined sheet pans. Bake for about 11 minutes. Cool the cookies for 5 minutes, then transfer to a rack. Repeat this process with the remaining dough.
Store the cookies in an airtight container for up to 4 days.