Grease and flour a 9x5-inch loaf pan and preheat the oven to 350 F.
In a large bowl, whisk together the dry ingredients (cocoa powder, flour, sugar, baking powder, baking soda, and salt).
Add the wet ingredients (eggs, buttermilk, oil, and vanilla extract) and mix until smooth.
Fold in ½ cup chocolate chips.
Pour the batter into the prepared pan, tap it on the counter a couple of times to level it out, and bake for one hour or until a toothpick inserted in the middle comes out clean. Let the bread cool down in the pan for 10 minutes, then transfer to a cooking rack to cool down completely.
Once the bread has cooled down, make the ganache: place 1/4 cup chocolate chips in a small bowl and set aside. Pour the heavy cream into a small saucepan and bring to a simmer. Turn of the heat and pour the cream over the chocolate chips. Let stand for a couple of minutes and stir until the chips are melted and the ganache is smooth.
Pour the ganache over the cooled bread.