Step 1: Preheat the Oven
Preheat your oven to 350°F (175°C) and grease the loaf pan with non-stick spray or butter.
Step 2: Mix the Dry Ingredients
In a mixing bowl, whisk together the flour, cocoa powder, sugar, baking powder, and salt until well combined.
Step 3: Combine the Wet Ingredients
In another bowl, mix the melted butter, eggs, and vanilla extract until smooth.
Step 4: Combine Wet and Dry Mixtures
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Be careful not to overmix. Fold in the chocolate chips if using.
Step 5: Layer the Fudge Sauce
Pour half of the brownie batter into the prepared loaf pan, spreading it evenly.
Drizzle half of the hot fudge sauce over the batter.
Pour the remaining brownie batter over the fudge layer and top with the remaining hot fudge sauce. Use a knife to swirl the fudge into the batter gently for a marbled effect.
Step 6: Bake the Bread
Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter). The top should look set and slightly cracked.
Step 7: Cool and Serve
Allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.
Dust with powdered sugar if desired, slice, and serve warm or at room temperature.