Melt chocolate and butter, using a microwave or a stovetop. When using the first, I microwave for 30 seconds, stir, then do it for another 15 to 30 seconds, and then stir until everything is melted. Let it cool for 5 minutes.
Mix brown sugar, eggs and espresso powder. Use a large bowl. Set aside.
Add the chocolate and butter mixture to the sugar mixture, and stir until combined.
Mix flour, milk powder, unsweetened Dutch cocoa powder, baking powder, baking soda, salt and 1 teaspoon of ginger.
Line a baking sheet with parchment paper or a silicone baking mat.
Add flour mixture into the chocolate mixture and mix until combined. Refrigerate for 20 minutes. The dough will appear sticky, but it will set.
Adjust your oven rack to the middle position (or upper middle if yours doesn’t have an exact middle position). Preheat it to 350°F.
Add granulated sugar into a bowl, and icing sugar into another bowl. Add ¼ teaspoon of ginger powder into the icing sugar, whisking to combine.
Scoop about 1 tablespoon of dough, rolling each into a ball using your hands.
Coat shaped cookies into the granulated sugar, lightly.
Coat then into the icing sugar, until every side is heavily covered.
Place each coated ball 2 inches apart on the baking sheet.
Bake cookies at 350°F for 10 to 11 minutes, until they are puffed and cracked. They are ready when the edges begin to set, but the center is still soft and shiny. They will look underdone in the middle, but they will continue to bake outside the oven.
Let cookies cool into the baking sheet for 2 minutes, then transfer them to a cooling rack.