Preheat oven to 350°F. Grease a 9x5-inch loaf pan and line with parchment, leaving overhang.
Whisk melted butter with granulated sugar and brown sugar.
Whisk in eggs one at a time, then vanilla.
Whisk flour, cocoa, baking powder, salt, and espresso powder (optional) in a separate bowl. Fold dry ingredients into wet until just combined.
Fold in ¾ cup chocolate chips, saving ¼ cup for topping.
Optional swirl: spread half the batter in the pan, dollop hot fudge, top with remaining batter, swirl gently.
Top with reserved chocolate chips.
Bake 45–60 minutes, until edges are set and a toothpick near the center comes out with moist crumbs. Tent with foil if browning too fast.
Cool in pan 20 minutes, then lift out and cool at least 1 hour before slicing.
Serve warm with hot fudge drizzle if desired.