In a heatproof bowl, combine the bittersweet and unsweetened chocolate. Place the bowl over a pot of simmering water, stirring occasionally until the chocolate is completely melted and smooth. Remove from heat and let it cool slightly.
In another bowl, whisk together the all-purpose flour, special dark cocoa powder, salt, and baking soda. Set this mixture aside for later.
In a large mixing bowl, beat the unsalted butter and dark brown sugar together until light and fluffy. This usually takes about 2-3 minutes with an electric mixer.
Add the eggs, one at a time, mixing well after each addition. Then, incorporate the vanilla and espresso powder, blending until combined.
Gradually add the dry ingredients to the wet mixture, mixing until just combined. Be careful not to overmix!
Gently fold the melted chocolate and chocolate chips into the dough until well incorporated.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheets. Press a Hershey’s Special Dark kiss into the center of each cookie. Chill the dough for at least 30 minutes in the refrigerator to help the cookies maintain their shape while baking.
Preheat your oven to 350°F (175°C). Bake the cookies for 10-12 minutes until the edges are set but the centers remain soft. Let them cool on the baking sheet for a few minutes before transferring to a cooling rack.
