In a mixing bowl combine the softened butter and powdered sugar and cream together using a wooden spoon, until smooth and uniform. Add the yolks, vanilla, and orange zest and mix until smooth and uniform.
Combine the flour, salt, 1 tbsp of the espresso powder, and the 2 tbsp Guittard Cocoa Rouge 22/24% Dutched Cocoa Powder (8oz) in a separate bowl and whisk together. Add the dry to the butter mixture and gently mix to incorporate, adding the 1-1/2 Cups Guittard Organic 74% Dark Couverture Chocolate Wafers (12oz) once the dries are about 50% incorporated.
Once the dough is uniform, turn it out onto a piece of parchment paper. Using your hands, shape the dough into a long rectangular log, or a cylinder if you prefer. If it’s sticky, you can dust your hands with a little flour. The log should be about 12” long and roughly 2 ½” wide.
Once shaped, wrap in the parchment and transfer to the fridge for at least 2 hours. You can also wrap well in plastic once fimly chilled, and keep in the fridge for up to one week.
To bake, heat the oven to 325°F with a rack in the middle. Line a sheet pan with parchment paper. Remove the dough from the fridge and let it soften slightly at room temperature so it’s easy to slice.
In a small bowl, whisk together the remaining espresso powder with the granulated sugar. Unwrap the dough and with a sharp knife, slice it into cookies about 1/2” thick.
Coat each cookie in the espresso sugar and transfer to the sheet pan, spacing the cookies about 2” apart.
Bake until just set, about 18 to 20 minutes. Transfer the cookies to a cooling rack and repeat with the remaining dough. These cookies will keep for up to 5 days in an airtight container.Enjoy!