Preheat oven to 350 degrees F. Line a metal 8-inch square pan with parchment paper.
In a large microwave-safe bowl combine 4 ounces (113 grams) of the chopped chocolate and butter. Microwave in 30-second bursts, stirring between each burst, until the mixture is melted and smooth. Add the sugar to the hot butter mixture and whisk vigorously until combined. Allow to cool until just barely warm.
Add in eggs, yolk, and vanilla extract and whisk by hand for about 1 minute, or until very well combined. This helps create that shiny crust on top.
Use a rubber spatula to stir in flour, cocoa powder, spices, and salt until just combined. Stir in the remaining 7 ounces (198 grams) of chocolate chunks and the candied ginger.
Pour into prepared pan and smooth out. Bake in the preheated oven for 30 minutes. Let cool in pan 30 minutes before slicing.