Ingredients

17 ounces 58% cacao chocolate pistoles 

10 ounces white chocolate calets 

5 ounces 38% cacao chocolate pistoles 

1/3 cup all-purpose flour 

2 tablespoons cake flour 

3 tablespoons cocoa powder (Dutch process) 

1 teaspoon Vietnamese extra-fancy cinnamon 

1/4 teaspoon baking powder 

1/4 teaspoon baking soda 

1/8 teaspoon cream of tartar 

1/4 teaspoon fine sea salt 

4 ounces unsweetened chocolate, chopped 

1/4 cup plus 1 tablespoon European-style butter 

3 large eggs 

3 large egg yolks 

1 1/3 cups plus 2 tablespoons superfine sugar 

1 1/8 teaspoons Trablit or pure coffee extract 

2 3/4 teaspoons pure vanilla extract 

1 cup coarse sanding sugar

Preparation

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.