Step 1: Prepare the Fudge Swirl

1. In a small microwave-safe bowl, combine the chocolate chips and heavy cream.
2. Microwave in 20-second intervals, stirring each time, until smooth and melted. Set aside to cool slightly.

Step 2: Make the Batter

1. Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan or line it with parchment paper.
2. In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.
3. In a large bowl, whisk the melted butter and sugar until smooth. Add the eggs and vanilla extract, mixing until well combined.
4. Gradually add the dry ingredients to the wet ingredients, alternating with the milk, starting and ending with the dry ingredients. Mix until just combined (do not overmix).

Step 3: Layer and Swirl

1. Pour half of the batter into the prepared loaf pan.
2. Drizzle half of the fudge swirl mixture over the batter and use a knife to gently swirl it through.
3. Add the remaining batter and top with the rest of the fudge swirl, repeating the swirling process.

Step 4: Bake the Bread

1. Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter).
2. Let the bread cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.