Make the cakes:

1. Prepare three 8-inch cake pans with parchment paper circles in the bottom, and grease the sides. Preheat oven to 350°F (180°C).
2. Combine the flour, cocoa powder, baking soda and salt in a medium sized bowl and set aside.
3. Add the melted butter, vegetable oil, sugars and vanilla extract to a large bowl and mix until well combined.
4. Add the eggs and sour cream and mix until well combined, then add the milk and mix until well combined.
5. Add the dry ingredients to the wet ingredients and mix just until well combined. Don’t over mix.
6. Add the hot water and mix until well combined.
7. Gently fold the shredded zucchini into the cake batter. Do not over mix.
8. Divide batter evenly between cakes pans and bake for 28-33 minutes, or until a toothpick comes out clean.
9. Remove cakes from oven and allow to cool for 3-4 minutes, then turn onto cooling racks to cool completely.

Make the frosting:

1. When the cakes are cooled, beat the butter in a large mixing bowl until smooth.
2. Add 3 cups (345g) of powdered sugar and the cocoa powder and mix until well combined and smooth.
3. Add the vanilla extract and 3 tablespoons of heavy cream and mix until well combined and smooth.
4. Add remaining 3 cups (345g) of powdered sugar and salt and mix until well combined and smooth.
5. Add remaining heavy cream until the frosting is the right consistency.

Assemble the cake:

1. Remove the cake domes from the tops of the cakes with a large serrated knife. See my tips on how to level a cake and how to stack a cake.
2. Place the first layer of cake on cake plate. Spread about 3/4 cup of frosting on top in an even layer.
3. Add the second layer of cake and add 3/4 cup of frosting on top in an even layer.
4. Add the final layer of cake on top and frost the outside of the cake. I left a rough/rustic/deckled top edge, but feel free to decorate how you like. You can press the mini chocolate chips into the bottom half of the sides of the cake and sprinkle a few on top, if you’d like as well.
5. Store cake well covered or in an air-tight container. You can leave it at room temperature for up to 24 hours, but then should refrigerate it. Serve at room temperature. Best if eaten within 3-4 days.