1/2 cup (4 ounces) unsalted butter
4 ounces good-quality bittersweet chocolate, coarsely chopped
1 cup all-purpose flour
1/2 cup unsweetened cocoa powder
2 teaspoons ground ginger
1 teaspoon ground cinnamon
1/2 teaspoon freshly grated ginger
1/2 teaspoon baking soda
1/2 teaspoon kosher salt
1 cup packed dark brown sugar
1/2 cup sugar
2 large eggs
2 teaspoons vanilla extract
Preheat the oven to 325°F. Line two baking sheets with parchment paper or silicone baking mats.
Combine the butter and chocolate in a double boiler (or heatproof bowl) set over simmering water and whisk occasionally until melted and smooth. Set aside until cooled but still liquidy.
Combine the flour, cocoa powder, ground ginger, cinnamon, grated ginger, baking soda, and salt in a medium mixing bowl and set aside.
In the bowl of a stand mixer fitted with the paddle attachment (or using an electric hand mixer), beat the brown sugar, granulated sugar, eggs, and vanilla on medium-low speed until well combined. Pour in the cooled chocolate mixture and continue to mix until the ingredients are evenly distributed. Add the dry ingredients to the mixing bowl and beat on low speed until just combined and no visible flour remains.
Scoop 12 balls of dough (preferably using a small ice cream scoop with a spring handle, about 1 1/2 tablespoon size) onto each parchment-lined baking sheet, leaving at least 1 to 1 1/2 inches of space between each cookie. Bake 1 pan of cookies at a time for 14 minutes, rotating the pan halfway through cooking time. (The cookies should be puffy and still fairly soft when removed from the oven.)
Immediately slide the cookies, still on the parchment paper, onto a wire cooling rack. Repeat with the second pan of cookies. Cool just a bit before serving, 5 to 10 minutes. Cookies can be stored in an airtight container for up to 3 days.