Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan with parchment paper.

In a large mixing bowl, beat together the softened unsalted butter and granulated sugar until light and fluffy.

Sift in the unsweetened cocoa powder, baking powder, and salt, mixing until well combined.

Incorporate the eggs one at a time, followed by the vanilla extract, mixing until fully combined.

Gradually add all-purpose flour and milk, alternating between the two while mixing until just combined.

Gently fold in the semi-sweet chocolate chips into the batter.

Pour half of the batter into the loaf pan, drizzle with half the hot fudge sauce, add the remaining batter, and top with the remaining fudge sauce.

Swirl the fudge sauce into the batter using a knife or skewer without overdoing it.

Bake in the preheated oven for 50-60 minutes until a toothpick inserted comes out with moist crumbs.

Let the bread cool in the pan for 10-15 minutes, then transfer to a wire rack to cool completely.

Serve warm or at room temperature, optionally with ice cream or mascarpone cheese.