1. Preheat oven to 350°F (175°C). Line a muffin pan with liners or grease well.

2. Grate 1 medium zucchini and pat with paper towels to absorb excess moisture.

3. In a large bowl, whisk together flour, cocoa powder, baking soda, and salt.

4. In another bowl, whisk eggs, both sugars, oil, sour cream, and vanilla until smooth.

5. Add the wet mixture to the dry ingredients and stir until just combined.

6. Fold in zucchini, chocolate chips, and white chocolate chunks.

7. Divide batter evenly into 12 muffin cups, filling each about 3/4 full.

8. Sprinkle extra chocolate on top if desired.

9. Bake for 18–22 minutes or until a toothpick comes out mostly clean.

10. Let muffins cool in the pan for 5 minutes, then transfer to a wire rack.