Preheat the oven to 350°F (175°C) and grease a loaf pan.

In a mixing bowl, sift together flour, cocoa powder, baking powder, and salt.

In a separate bowl, mix buttermilk, melted butter, and sugar until combined. Add eggs one at a time.

Fold dry ingredients into wet mixture until just combined.

Fold hot fudge sauce into the batter, adding optional mix-ins if desired.

Pour batter into the loaf pan and bake for 50-60 minutes. Check with a toothpick for doneness.

Let the bread cool in the pan for 10 minutes, then transfer to a wire rack.