Preheat your oven to 350°F (175°C).
In a mixing bowl, combine whole wheat flour, cocoa powder, baking powder, and salt.
In another bowl, whisk together the applesauce, honey (or maple syrup), eggs, and vanilla extract.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined.
Fold in the dark chocolate chips if using.
Pour the batter into a greased loaf pan.
Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes before transferring it to a wire rack.