Preheat your oven to 350°F (175°C). Grease and line a 9×5-inch loaf pan with parchment paper, ensuring there is overhang for easy removal.
In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined.
In a large bowl, cream the softened butter and granulated sugar together until the mixture is light and fluffy, which should take about 3-4 minutes. Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.
Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk, starting and ending with the dry ingredients. Mix until just combined.
Carefully fold in the hot fudge sauce and chocolate chips, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared loaf pan and bake for 55-60 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs attached.
Allow the bread to cool in the pan for 10 minutes before removing it to a wire rack. While still warm, drizzle the top with additional warmed hot fudge sauce and sprinkle with chocolate chips and nuts if desired.
