Get your holiday chocolate fix with this rich treat from Malika Ameen, a former contestant on Bravo's "Top Chef: Just Desserts."
Place 5 ounces of 58% cacao, white chocolate, and 38% cacao on a cutting board; very coarsely chop chocolate, leaving a third of the pieces whole. Set aside.
In a large bowl, whisk together both flours, cocoa powder, cinnamon, baking powder, baking soda, cream of tartar, and salt; set aside.
Set a heatproof bowl over (but not touching) simmering water. Add remaining 12 ounces 58% cacao, unsweetened chocolate, and butter; let melt, stirring, until well combined.
Transfer chocolate to the bowl of an electric mixer fitted with the paddle attachment. Add eggs and yolks; blend until just combined. Add superfine sugar, Trablit, and vanilla; mix to combine. Add flour mixture and mix to just combine, scraping down sides of bowl as necessary. Add reserved chopped and whole chocolate pieces; mix to just incorporate. Cover and transfer dough to refrigerator to chill for 30 minutes.
Preheat a convection oven to 325 degrees or a conventional oven to 350 degrees. Line baking sheets with nonstick baking mats.
Place sanding sugar in a shallow dish. Fill a second shallow dish with water. Using a 3/4-ounce ice cream scoop, scoop out dough; press down on tops of dough with your thumb. Dip bottom of each portion of dough in water and then in sanding sugar; place on prepared baking sheets.
Transfer to oven and bake for 4 minutes in a convection oven or 3 minutes for a conventional oven. Rotate baking sheet and continue baking until cookies are just set (they will still look slightly wet), about 3 minutes for convection or 2 to 3 minutes for a conventional oven. Let cookies cool on baking sheets.
Cookies can be stored in an airtight container at room temperature for up to 5 days or frozen for up to 1 month.