Preheat oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment paper, leaving a slight overhang for easy removal.
In a large bowl, whisk together eggs, brown sugar, granulated sugar, vanilla, and oil until fully combined and smooth.
Sift in flour, cocoa powder, baking soda, and salt. Stir gently until just combined. Do not overmix.
Fold in chocolate chips. The batter will be thick and fudgy.
Spread half of the batter into the prepared pan. Spoon the hot fudge over the batter layer (avoid edges). Top with the remaining batter and gently swirl with a knife if desired.
Bake for 50–60 minutes. A toothpick inserted in the center should come out with moist crumbs. Tent with foil if the top is browning too fast.
Cool in the pan for 20 minutes, then lift out and cool completely on a wire rack before slicing.
Optional: Warm slices before serving and drizzle with extra fudge or top with ice cream for a decadent treat.