Tool

• Stand mixer

• Three 8‑inch cake pans

Ingredients

For the cake

• 3 cups all‑purpose flour (360g)

• 1 cup unsweetened natural cocoa powder (100g)

• 1 tablespoon baking soda

• ¾ teaspoon baking powder

• 1½ teaspoons espresso powder (optional)

• ¾ teaspoon salt

• 1½ cups vegetable oil (354mL)

• 1½ cups granulated sugar (300g)

• 1 cup light brown sugar, packed (220g)

• 6 large eggs, room temperature

• ½ cup sour cream, room temperature (120g)

• 1 tablespoon vanilla extract

• 4½ cups grated zucchini (about 3 medium) (475g)

• 1½ cups semi‑sweet chocolate chips (270g)

For the buttercream

• 1 cup semi‑sweet chocolate chips (180g)

• ⅔ cup heavy cream, divided (160mL)

• 5½ cups powdered sugar (660g)

• 1½ cups unsalted butter, room temperature (282g)

• ½ teaspoon salt

• ⅓ cup unsweetened natural cocoa powder (33g)

• 1½ teaspoons vanilla extract

Direction

For the cake

• Preheat oven to 350ºF. Grease three 8‑inch pans, line bottoms with parchment, and wrap with soaked baking strips if available.

• Whisk flour, cocoa, baking soda, baking powder, espresso powder, and salt; set aside.

• In another bowl, whisk oil, granulated sugar, brown sugar, eggs, sour cream, and vanilla until smooth.

• Fold grated zucchini into wet mixture.

• Add wet mixture to dry mixture; stir until almost combined.

• Add chocolate chips; stir until no dry streaks remain.

• Divide batter evenly (about 3⅓ cups / 810g per pan).

• Bake 35–40 minutes, until centers are springy and edges pull away.

• Cool in pans for 10 minutes, then invert onto a wire rack. Remove parchment and cool completely.

For the buttercream

• Melt chocolate chips with ⅓ cup heavy cream in microwave, stirring every 30 seconds. Cool slightly.

• Cream butter and salt on medium for 3 minutes until light and creamy.

• Sift in cocoa powder; mix on low until combined.

• Add powdered sugar gradually, alternating with remaining cream.

• Add vanilla and melted chocolate.

• Beat on medium for 2 minutes until fluffy.

• Transfer 1 cup (236g) to a piping bag fitted with Ateco 869.

For the assembly

• Place first cooled layer on a stand; spread 1 cup buttercream evenly.

• Add second layer; repeat.

• Add final layer top‑side down for a flat finish.

• Frost top and sides, scraping sides for a “naked cake” look.

• Pipe buttercream dollops around the top edge.

• Chill cake for 30 minutes before slicing for cleaner cuts.

Notes

• Chill the cake before slicing — 30 minutes firms the frosting for clean cuts.

• Feeding a crowd? Use proper round‑cake slicing technique to maximize servings.

Nutrition

Calories: 1285kcal Carbohydrates: 150g Protein: 12g Fat: 75g Saturated Fat: 33g Polyunsaturated Fat: 18g Monounsaturated Fat: 19g Trans Fat: 1g Cholesterol: 166mg Sodium: 600mg Potassium: 607mg Fiber: 8g Sugar: 113g Vitamin A: 1194IU Vitamin C: 8mg Calcium: 116mg Iron: 6mg