Preheat the Oven – Set your oven to 350°F (175°C). Grease a 9×5-inch loaf pan and line it with parchment paper for easy removal.
Mix Dry Ingredients – In a bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
Mix Wet Ingredients – In a large bowl, stir melted butter and sugar until smooth. Add eggs one at a time, mixing well. Stir in vanilla.
Combine and Fold – Gradually mix dry ingredients into the wet mixture until just combined. Fold in chocolate chips.
Bake – Pour batter into the pan, smooth the top, and bake for 40–45 minutes. A toothpick should come out with a few moist crumbs. Cool in the pan for 10 minutes, then transfer to a rack.
Make the Hot Fudge – Heat heavy cream in a saucepan until it simmers. Remove from heat, add chocolate chips, butter, and vanilla, then stir until smooth and glossy.