Step 1: Preheat the Oven and Prepare the Pan

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

Step 2: Mix the Dry Ingredients

In a medium bowl, sift together the all-purpose flour, cocoa powder, baking powder, and salt. Sifting ensures a smooth batter and avoids lumps in the cocoa powder. Set aside.

Step 3: Combine the Wet Ingredients

In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until well combined. Add the eggs, one at a time, whisking until smooth after each addition. Stir in the vanilla extract.

Step 4: Alternate Adding Dry Ingredients and Milk

Gradually add the dry ingredients to the wet ingredients in three additions, alternating with the milk. Start and end with the dry ingredients, mixing gently after each addition until just combined. Avoid overmixing, as this can result in a denser loaf.

Step 5: Fold in the Chocolate Chips

Using a spatula, gently fold the semi-sweet chocolate chips into the batter. This adds pockets of melted chocolate throughout the bread.

Step 6: Layer and Swirl the Hot Fudge

Pour half of the batter into the prepared loaf pan and spread it evenly. Drizzle half of the warmed hot fudge sauce over the batter. Add the remaining batter on top and drizzle the rest of the hot fudge sauce. Use a knife or skewer to gently swirl the fudge into the batter, creating a marbled effect.

Step 7: Bake

Place the loaf pan in the preheated oven and bake for 45-55 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter). Check the bread at the 40-minute mark, and if the top is browning too quickly, cover it loosely with foil for the remaining baking time.

Step 8: Cool and Serve

Allow the bread to cool in the pan for 15 minutes, then use the parchment paper overhang to lift it out of the pan and onto a wire rack. Let it cool completely before slicing (if you can resist!).