Step 1

Preheat the oven to 350ºF. Line baking sheets with parchment paper.

Step 2

In a microwave-safe bowl, microwave chocolate in 20-second bursts until melted, stirring between each burst. Set aside to cool until just warm (about 80°F).

Step 3

In a medium bowl, whisk together the flour, cocoa powder, espresso powder, baking soda, and salt. Set aside.

Step 4

In a large bowl, use an electric mixer on medium-high speed to beat the butter, granulated sugar, and brown sugar on medium-high speed until light and fluffy, about 2 to 3 minutes. Add in the cooled, melted chocolate and beat until combined. Add the egg, egg yolk, and vanilla extract and beat until completely smooth and combined. Scrape down the sides and bottom of the bowl as needed. Slowly beat in the flour mixture. Fold in the chocolate chips with a rubber spatula. Dough will be sticky.

Step 5

Using a medium spring-loaded scoop, drop 1 1/2-tablespoon balls of dough onto prepared baking sheets, spacing 2 inches apart. Wet your hands slightly, then roll each dough ball between your palms to smooth.

Step 6

Bake for about 10 minutes or until set. Cool for 5 minutes before removing to wire racks to cool completely.

Step 7

In a small bowl, use a small whisk or a fork to combine the powdered sugar and coffee liqueur until a thick but pourable glaze forms. Place a sheet of parchment paper underneath the cooling racks to catch the glaze for easier clean-up. Drizzle glaze all over cooled cookies. Allow to set.

Step 8

Store the cookies between layers of parchment paper in an airtight container at room temperature for up to 3 days.