01 -
Preheat oven to 350°F. Grease a 9x5-inch loaf pan with non-stick baking spray and line with parchment paper, leaving the edges overhanging for easy removal.
02 -
Using a box grater, shred a medium to large zucchini to yield about 1 3/4 cups loosely packed zucchini. Wrap in paper towels or a dishcloth to pat dry and set aside.
03 -
In a large bowl, whisk the melted butter and granulated sugar together until pale and well combined.
04 -
Mix in the egg followed by the egg yolk until fully incorporated. Add vanilla extract and sour cream; whisk to combine.
05 -
Stir in the prepared shredded zucchini until evenly distributed in the mixture.
06 -
In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.
07 -
Add the dry ingredients to the zucchini mixture in two additions. Gently fold using a spatula or wooden spoon. Avoid overmixing.
08 -
Gently stir in the semi-sweet chocolate chips until evenly distributed in the batter.
09 -
Pour the batter into the prepared loaf pan. Sprinkle additional chocolate chips on top for decoration.
10 -
Bake for 45–50 minutes, checking halfway through. If the top is browning too quickly, cover loosely with aluminum foil. Bake until a toothpick inserted into the center comes out clean or with a few crumbs.
11 -
Allow the bread to cool in the pan for 20–30 minutes. Use the parchment paper overhangs to lift it out and transfer to a wire rack. Cool completely before slicing, or serve warm.