Preheat your oven to 350°F (175°C). Prepare your loaf pan by lining it with parchment paper and lightly greasing it with butter or cooking spray.
In a small bowl, combine the instant coffee granules with the hot water. Stir until the granules are fully dissolved. Set aside to cool.
In a large mixing bowl, cream together the room temperature butter, granulated sugar, and brown sugar using a stand mixer or hand mixer until light and fluffy. This should take about 3-5 minutes.
Add the eggs one at a time, mixing well after each addition. Then, stir in the vanilla extract and the cooled melted chocolate, blending until smooth.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and kosher salt. Gradually add this dry mixture to the wet ingredients, alternating with buttermilk. Start and end with the dry ingredients. Mix until just combined; do not overmix.
Pour in the dissolved coffee mixture and gently fold it into the batter. Be careful not to overmix.
Fold in the chocolate chips for added richness and texture.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula. Bake in the preheated oven for 60-70 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and allow it to cool in the pan for about 15 minutes. Then, transfer it to a cooling rack to cool completely.
Once cooled, dust the cake with powdered sugar or drizzle with chocolate ganache for an elegant finish. Slice and serve to your delighted guests!