Preheat your oven to 350°F and grease a 9x13 inch baking dish or similar size cake pan. While the oven heats, sift together the flour, cocoa powder, baking soda, baking powder, salt, and instant espresso powder in a medium bowl. Sifting the cocoa is crucial here—it removes lumps and ensures even chocolate distribution throughout the cake. Set this dry mixture aside.

While the oven continues heating, shred your zucchini and place it in a clean kitchen towel or cheesecloth. Squeeze it firmly to remove as much excess moisture as possible—this is essential because too much water will make your cake dense and soggy. In a large mixing bowl, whisk together the sugar, buttermilk, room temperature eggs, and vanilla until well combined and slightly pale. I always use room temperature eggs because they emulsify better with the other ingredients, creating a more tender crumb.

Add the dry ingredient mixture from Step 1 to the wet mixture from Step 2, stirring gently with a spatula until just combined—don't overmix, as this can develop gluten and make the cake tough. Fold in the squeezed zucchini until evenly distributed throughout the batter. The batter should be thick and chocolatey with visible zucchini pieces.

Pour the batter into your prepared pan and spread it into an even layer. Bake at 350°F for 30-35 minutes, until a toothpick inserted in the center comes out with just a few moist crumbs (not wet batter). The cake will continue to set slightly as it cools. Remove from the oven and let it cool completely in the pan at room temperature—this usually takes about an hour.

While the cake cools, prepare your frosting. In a clean, cold mixing bowl, combine the heavy cream, powdered sugar, cocoa powder, vanilla, and instant espresso powder. I always use heavy cream from quality brands like Land O'Lakes because it whips to a more stable, luxurious texture. Start beating on medium speed and gradually increase to medium-high, beating until stiff peaks form. Be careful not to overbeat or you'll end up with butter—stop as soon as the peaks hold their shape.

Once the cake has cooled completely, spread the whipped cream frosting evenly over the top using an offset spatula or the back of a spoon. For a prettier presentation, create gentle swirls or peaks in the frosting. Slice and serve immediately, or refrigerate for up to a few hours if needed—the whipped cream frosting is best enjoyed fresh but will hold well chilled.