This recipe for Zucchini Chocolate cake is extremely moist and tender with tart hibiscus buttercream.
Preheat oven to 350 degrees. Grease and flour three 8-inch round cake pans. Line with a parchment paper. Set aside. In a large bowl sift together flour, cocoa, baking soda, and salt. Set aside. In the bowl of a stand-up mixer beat eggs, With the mixer running, slowly add sugar and mix until light yellow in color. Slowly add olive oil, buttermilk, and vanilla. Mix until smooth and light in color. Beat in flour and cocoa mixture until smooth. Fold in grated zucchini then boiling water. Pour batter into prepared baking sheet and place in the preheated oven. Bake for 30 minutes or until cake springs back when lightly touched. Remove from oven and cool for 5 minutes. Invert cakes onto a cooling rack until completely cool OR for a moister cake immediately wrap in plastic and wrap and place right into a freezer. Can be frozen for several days, or place in a refrigerator until completely cool before using.
In a very clean bowl of an electric mixer, add egg whites and sugar. Place over a simmering pot of water, stirring constantly until temperature reaches 160 degrees F. Rub a small amount of the mixture between two fingers to make sure the sugar is dissolved. Remove from heat. Using the whisk attachment, beat until the mixture is a thick meringue and the bottom of the bowl is cool to the touch. The bowl must be cool before adding the butter. Replace the whisk with the paddle attachment. With the mixture on medium-low speed add butter once slice at a time until all of the butter has been incorporated. The mixture should be silky smooth and thick. The mixture may begin to look curdled, keep mixing until it is smooth. This can take 10 minutes or so. Mix in salt and vanilla.
Replace the whisk with the paddle attachment. With the mixture on medium-low speed add butter one slice at a time until all of the butter has been incorporated. The mixture should be silky smooth and thick. The mixture may begin to look curdled, keep mixing until it is smooth. This can take 10 minutes or so. Mix in salt and vanilla. Add blackberry puree, if using. Once the puree is added keep mixing until the mixture is silky again.
This little step will help you create extremely moist cakes every time. While the cakes are still hot (YES! still hot) wrap each one in plastic wrap and place in the freezer. I like to make my cakes ahead of time, so this tip works. They will keep in the freezer for quite a while. If storing for more than a few days, wrap in plastic THEN wrap in foil. The cakes will keep for weeks.
If you want to use the cakes the same day, wrap in plastic wrap and cool in the refrigerator for a few hours. Make sure the cakes are completely cold before icing.