01 -
Preheat the oven to 350°F. Use parchment to line a 9x5-inch loaf pan, then grease it lightly.
02 -
Combine butter and both sugars in a bowl. Mix in eggs and vanilla. Gently fold in flour, cocoa, baking powder, salt, and chocolate chips.
03 -
Start by pouring half the batter into the loaf pan. Drizzle fudge on top, and use a knife to swirl. Add the rest of the batter, giving it another swirl.
04 -
Bake for roughly 50-55 minutes, checking with a toothpick for slightly sticky crumbs. Cover loosely with foil if the top browns too much.
05 -
Let it cool in the pan for about 10-15 minutes, then transfer to a rack. If you'd like, sprinkle with cocoa or powdered sugar, or decorate with toppings.