Ingredients:

  • 2 cups (250g) all-purpose flour (spooned & leveled)
  • ¾ cup (62g) unsweetened natural cocoa powder
  • 2 teaspoons baking soda
  • ½ teaspoon baking powder
  • 1 teaspoon espresso powder (optional, but highly recommended!)
  • ½ teaspoon salt
  • 1 cup (240ml) canola or vegetable oil
  • 1 cup (200g) granulated sugar
  • ¾ cup (150g) packed light or dark brown sugar
  • 4 large eggs, at room temperature
  • ⅓ cup (80g) sour cream or plain yogurt, at room temperature
  • 2 teaspoons pure vanilla extract
  • 3 cups (about 360g) shredded zucchini (lightly blotted; about 2 medium)
  • 1 cup (180g) semi-sweet chocolate chips (regular or mini)
  • 1 ¼ cups (282g) unsalted butter, softened to room temperature
  • 3 ½ cups (420g) confectioners' sugar
  • ¾ cup (62g) unsweetened cocoa powder (natural or Dutch-process)
  • 3-5 tablespoons (45-75ml) heavy cream (or half-and-half or whole milk), at room temperature
  • ¼ teaspoon salt
  • 1 teaspoon pure vanilla extract
  • Chocolate chips and/or chocolate sprinkles (optional)

Instructions:

  1. Preheat oven to 350°F (177°C). Grease and flour two 9-inch round cake pans, line with parchment paper circles, and grease the parchment again.
  2. In a large bowl, whisk together the flour, cocoa powder, baking soda, baking powder, espresso powder (if using), and salt.
  3. In another large bowl, using an electric mixer, beat together the oil, granulated sugar, brown sugar, eggs, sour cream, and vanilla extract until well combined.
  4. Add the shredded zucchini to the wet ingredients and mix until just combined.
  5. Gradually add the dry ingredients to the wet ingredients, mixing on medium speed until just combined. Be careful not to overmix.
  6. Gently fold in the chocolate chips.
  7. Divide the batter evenly between the prepared cake pans. Bake for 28-32 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
  8. Let the cakes cool in the pans for 1 hour, then invert onto a cooling rack to cool completely. The cakes must be completely cool before frosting.
  9. In a large bowl, using an electric mixer, beat the softened butter until creamy. Gradually add the confectioners' sugar and cocoa powder, mixing on low speed until combined.
  10. Add 3 tablespoons of the heavy cream, salt, and vanilla extract. Beat on low speed for 30 seconds, then increase to high speed and beat until smooth and creamy. Adjust cream to reach desired consistency.
  11. Level the cakes. Using a serrated knife, trim the tops of the cooled cakes to create a flat surface.
  12. Place one cake layer on a serving plate or cake stand. Spread with a generous amount of frosting. Top with the second cake layer.
  13. Frost the top and sides of the cake with the remaining buttercream.
  14. Decorate with chocolate chips, sprinkles, or piping as desired.
  15. Slice and serve. Store leftovers in an airtight container at room temperature for up to 2 days, or in the refrigerator for up to 5 days.