Pre-heat the oven to 350°F . Spray a 9 x 5 loaf pan with nonstick spray.
In a large bowl, mash the bananas. Then whisk in the brown sugar, melted butter, vanilla and egg. Sift in the salt, flour, baking soda and cocoa powder; stir the batter with a wooden spoon until well incorporated. Gently stir in the semi-sweet chocolate chips.
Spread the batter into the prepared pan; then, evenly sprinkle the milk chocolate chips.
Place in the oven and bake for 50 to 55 minutes, or until a toothpick inserted in the middle of the bread comes out clean.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Slice and serve.