Step 1: Prepare the Loaf Pan

1. Preheat your oven to 350°F (175°C).
2. Grease a 9×5-inch loaf pan with butter or nonstick spray and line it with parchment paper, leaving overhangs for easy removal.

Step 2: Make the Batter

1. In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth.
2. Add the eggs and vanilla extract, whisking until fully combined.
3. Sift the flour, cocoa powder, baking powder, and salt into the wet ingredients. Gently fold the dry ingredients into the wet mixture until no streaks remain. Avoid overmixing.
4. Stir in the chocolate chips, reserving a few for topping if desired.

Step 3: Add the Hot Fudge Swirl

1. Pour half of the batter into the prepared loaf pan, spreading it evenly with a spatula.
2. Drizzle the hot fudge sauce over the batter, then gently swirl it with a knife or skewer.
3. Add the remaining batter on top, smoothing it out with a spatula. Swirl in additional hot fudge if desired.

Step 4: Bake

1. Bake the loaf in the preheated oven for 50–55 minutes, or until a toothpick inserted into the center comes out with moist crumbs (but no wet batter).
2. If the top begins to brown too quickly, tent the loaf with aluminum foil during the last 10 minutes of baking.

Step 5: Cool and Serve

1. Allow the bread to cool in the pan for 10–15 minutes before transferring it to a wire rack to cool completely.
2. Slice and serve as is, or garnish with powdered sugar, mini chocolate chips, or a drizzle of warm fudge sauce.