Step 1

Preheat oven to 350 degrees. Coat a 9 x 13 metal baking pan with nonstick spray. Set aside.

Step 2

In a large mixing bowl, sift together dry ingredients: flour, cocoa powder, baking soda. baking powder, salt and espresso powder. Set aside.

Step 3

In a separate bowl, use an electric mixer to beat together oil and both sugars.

Step 4

Add eggs, one at a time, beating after each addition until well incorporated.

Step 5

Beat in sour cream, vanilla and grated zucchini until combined.

Step 6

Gradually add dry ingredients to wet, beating on medium speed until just combined. Do not overmix.

Step 7

Add chocolate chips, stirring with a wooden spoon until evenly distributed.

Step 8

Pour batter into prepared baking pan and bake for 45 minutes. Cake is done when a tester inserted into the center comes out clean.

Step 9

Place baking pan on a wire rack to cool completely, approximately 2 hours, before frosting with chocolate buttercream.

Step 10

Beat butter with an electric mixer on medium speed until creamy and smooth, approximately 2 minutes. Scrape down the sides of the bowl with a spatula as needed.

Step 11

Add powdered sugar, cocoa powder, vanilla, heavy cream and salt beating on low until incorporated then increase speed to high and beat until fluffy, approximately 2 minutes.

Step 12

Frost cake with buttercream then top with chopped chocolate if desired.

Step 13

For pristine slices, clean knife blade with hot water in between cuts.

Step 14

Cake will keep covered at room temperature up to 3 days or refrigerated up to 5 days.