Chocolate Zucchini Loaf Cake with Chocolate Icing is rich, moist, and deeply chocolatey, thanks to grated zucchini that keeps it soft. Finished with a sweet, glossy chocolate icing, it’s the perfect simple dessert or snack.
Prep the pan: Preheat oven to 350°F (175°C). Grease and line an 8x4-inch loaf pan with parchment paper.
Mix the dry ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking soda, baking powder, salt, and espresso powder.
Make the batter: In a large bowl, whisk together the brown sugar, oil, eggs, vanilla, and milk until smooth and emulsified.
Fold in zucchini: Stir in the grated zucchini and chocolate chips (if using) until evenly distributed.
Combine & bake: Add the dry ingredients to the wet and fold gently until just combined. Pour the batter into the prepared pan and smooth the top. Bake for 45–55 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs.
Cool the cake: Let the loaf cool in the pan for 10–15 minutes, then transfer to a wire rack to cool completely.
Make the chocolate icing: In a medium bowl, whisk together the boiling water and cocoa powder until smooth. Add the softened butter and vanilla, then beat in the powdered sugar gradually until smooth and glossy. The icing should be thick but pourable—add a splash more water if needed.
Ice the cake: Once the cake is fully cool, spread the icing generously over the top and let it set for 15–20 minutes before slicing.