Lightly grease a 9×5 loaf pan with butter or line with parchment paper, and set aside.
Preheat your oven to 350°F (175°C).
In a large bowl, whisk together the flour, baking powder, baking soda, salt, and cocoa powder.
In another bowl, combine the cup of sourdough starter, sugar, butter or oil, eggs, vanilla, and milk. Mix until well combined.
Add the wet ingredients to the dry ingredients and stir until just combined. Do not overmix.
Mix the chocolate chips in and any other add-ins.
Pour the sticky dough in the prepared pan.
Bake in the preheated oven for about 55-65 minutes, or until a toothpick inserted into the center of the bread comes out clean. If the top starts to brown too quickly, you can cover it loosely with aluminum foil.
Serve warm, or let the sweet bread cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.
Slice and enjoy your homemade bread!