1. Preheat your oven to 350 F (175 C). Grease and flour a 9×5-inch loaf pan, or line it with parchment paper, leaving an overhang on the sides for easy removal.

2. In a large mixing bowl, whisk together the active sourdough starter, granulated sugar, melted butter, egg, and vanilla extract until well combined and smooth.

3. In a separate medium bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, and unsweetened cocoa powder.

4. Gradually add the dry ingredients to the wet ingredients, alternating with the milk. Begin and end with the dry ingredients. Mix until just combined; do not overmix.

5. Gently fold in the shredded coconut and chocolate chips until they are evenly distributed throughout the batter.

6. Pour the batter into your prepared loaf pan, spreading it evenly with a spatula. If desired, sprinkle the turbinado sugar over the top of the batter.

7. Bake for 45-50 minutes, or until a wooden skewer or toothpick inserted into the center of the loaf comes out clean.

8. Once baked, remove the loaf from the oven and let it cool in the pan for about 10-15 minutes before carefully transferring it to a wire rack to cool completely.