In a small bowl, combine the instant coffee granules with the hot water. Stir until the coffee granules are fully dissolved. Set aside to cool.
In a large mixing bowl, cream together the room temperature butter, granulated sugar, and brown sugar until light and fluffy. This usually takes about 3-5 minutes. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and the cooled coffee mixture.
In another bowl, whisk together the flour, cocoa powder, baking powder, and salt until well combined.
Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk. Start and end with the dry ingredients. Mix until just combined. Be careful not to overmix, as this can result in a dense cake.
Gently fold in the melted chocolate and chocolate chips using a rubber spatula until evenly distributed throughout the batter.
Pour the batter into your prepared pound cake pan, smoothing the top with a spatula. Bake in a preheated oven at 350°F (175°C) for about 60-70 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for about 15 minutes. Then, transfer it to a cooling rack to cool completely. Once cooled, dust with powdered sugar or drizzle with chocolate ganache before slicing and serving.